league-of-legends
I found this nice map that indicates where players can Flash across walls.
Unfortunately, the range for Flash has been reduced, most recently in the V1.0.0.129 patch in November, 2011. Since this image has no timestamp (and shows the old map textures), it's difficult to determine if it's still up-to-date.
So which sections of walls are still Flashable? And which sections are tricky to Flash over?
I don't consider Nasus a true tank - he has no real Tank abilities, and serves better as a Tanky DPS / Anti-carry. That said, here's a list of the heroes I consider true tanks in the current metagame.
I'll grant you that Alistar's hard to play optimally, but when he is, the bull's a force to be reckoned with. Two hard CCs (neither affected by Merc Treads). Triumphant Roar makes him an excellent pusher, and his Ultimate and high base health make you an excellent damage soak. Additionally, little of his power comes from items; Pulverize + Headbutt is really good even without any bonus from AP.
Amumu's got two major things going for him: He's a great initiator, and he's a tank who can jungle and gank effectively. Due to the experience bonus, most top teams have a jungler on Summoner's Rift, and Amumu's one of the better ones. He also has two hard CCs in bandage toss and his ult, which can make escaping from him quite difficult (not to mention keeping folks within Despair for longer)
Poor Cho just get nerfed pretty bad in the Nocturne patch, losing substantial damage numbers from feast. That aside, he still is a decent (if not a first pick) tank with a skill shot initiation ability (though Rupture is more easily dodge-able than some other initiators) and an AoE silence. There's also something to be said for the psychological and mechanical effects of having the largest model on the screen. You'll be shielding your allies from attacks simply because your opponents can't find them to click under a fully-feasted Cho'gath. After you've maxed your feast stacks, try using Feast earlier in fights rather than later: it does true damage, and it's a pretty sizeable nuke - carries especially tend to panic when 1/4 of their health (or more) suddenly vanishes.
Mana-regen problems aside, Galio is a strong Tank. His most notable skills are his Ult and his Gust -- an AoE taunt nuke is especially powerful when combined with other AoE ults, such as Annie, Amumu, Morgana, Malphite, etc. Gust is useful both as a chasing mechanic and to help allies escape. Unfortunately, opposite-but-otherwise-like Rammus, Galio's usefulness tends to diminish in matches with primarily physical damage where he can't make full use out of his passive.
Garen is not a "typical" Tank, and works best as an Offtank due to not having a strong initiator or CC other than his silence (which is pretty useful in and of itself). Garen's a tough character who can bring a lot of damage to a group of enemies between judgement and his iconic sunfire cape. His ult is interesting, as it can be difficult to judge when to best use it, though some players dislike it because of its tendency to "steal" kills.
Gragas gets a damage reduction, an AoE Slow, Area Denial, and a massive radial knockback on a relatively short cooldown. He works well as a tank (consider starting with a rod of ages) because of fight disruption alone, and drunken rage and happy-time give him quite a long longevity as well, making him a passable pusher.
Malphite joins Cho in having been hit with the nerf-bat in the last patch, but is still a strong tank. Like Amumu, Rammus, and Shen, Malphite can jungle effectively, and has a combination of an impressive initiator, and a damage-dealing skill that scales off of armor (so even building straight tank items, you can deal a hefty sum of damage). With his Q, he can be especially effective by tunnel-visioning enemy carries.
Maokai is a great tank based around team fights. His ultimate is an AoE damage reduction, which when strategically placed, can turn the tide of fights. He has a snare, which is great to gank with, or focus down the enemy carry, a small AoE slow, and a really strong harass with his ranged sapling. His passive makes him have a very strong laning presence. After every 5 abilities, his next auto attack heals him 7% hp. This is also a incredibly useful skill in team fights, giving him huge survivability potential.
Mordekaiser can be an incredible tank, especially if he gets a few early kills and gets an item and level advantage over the other players. Though I've heard of folks jungling as Mordekaiser, I prefer to see him in a solo lane, where a good player can easily 2 v 1 by abusing Iron Man (well, perhaps less easily, depending on the opponents, but I've seen it done across a number of games). Make sure to get some AP to go with the Kaiser - Rylai's or an Abyssal Scepter and Sorc Boots make for a very offensive tank, especially in the laning phase where his short cooldowns make for an easy harass.
When built properly, Nunu makes a great off-tank. The thing you have to realize about Nunu is that the slow on his E is insane. It's 70% I think at rank 5? If Nunu catches up to you alone, you are not getting away from him if he has the mana to continually iceball you. Also important to note is Consume - the health it restores is not insubstantial, and with a Will of the Ancients, you can easily recover half your health every 10 seconds or so.
Rammus has everything a tank needs - a damage reduction ability (defense curl), an intiator paired with a slow (powerball), hard CC and target peeling (taunt), and team fight presence (tremors adds up fast!). Did we mention that he could jungle and his taunt has a relatively quick cooldown? A top pick for sure.
Shen is probably up in the top 3 with Amumu and Rammus when it comes to tanks (in my mind at least). If you can learn to correctly handle his Energy (which can be a little tricky to get the hang of at first), a good Shen player can be phenomenal. He's got a damage shield, an AoE Taunt, and a global ult / ally savior mechanic. One thing to note is that you don't want to build dodge on Shen - build armor/MR and health instead: it makes his passive come up more often and for more damage.
Finally, Singed. Singed is known for running really fast - make sure to take ghost, as it lets you spread your poison much more handily without having to path around enemies. As singed, you want your opponents to chase you; with your ult you're more than likely faster than them (and insanity potion lasts for an unmatched THIRTY SECONDS) and they'll kill themselves on your poison trail if they chase you for too long. Of course, when they finally break off, that's when you turn around, stick 'm with your adhesive, and then fling 'm behind you into more poison. Fling is an okay initiator, though it takes practice to make sure you're not accidentally throwing the enemies away from your team.
The following champions are considered support champions, in the sense that they will either heal/shield an ally and/or buff their armor/magic resist/movement speed.
Janna excels in supporting teams.
She has many support abilities:
Howling Gale which launches enemies into the air in a line.
Eye of the Storm shields an ally for a determined amount of damage and gives a damage buff, and it is the only shield capable of protecting turrets.
Moonsoon is a teamfight changer ability as it aoe heals your team and blows away enemies in Janna's ability ratioJanna as also a natural passive that is buffs the movement speed of your whole team.
Tailwind grants 3% move speed buff! 
Karma can contribute with great magic damage bursts. Additionally, she has a single target movement speed buff. Karma is a special support champ in the sense that she does not posses an ultimate ability per se, but her ult, Mantra, gives her a bonus effect on all of her other 3 spells:
Heavenly Wave + 
Mantra = AOE Heal in a cone in front of Karma
Spirit Bond + Mantra = Single Target Move Speed Buff x 2
Soul Shield + Mantra = Very High Scaling shield + Aoe Magic Damage around the shield bearer, in my opinion her best ability of all. 
Kayle makes an ally invulnerable to all damage for 2-3 seconds! Additionally, she heals allies and slows enemies, making her a very nice support pick. Unlike Janna and Karma which build defensive and AP items, Kayle builds Hybrid items like Hextech Gunblade and Guinsoo RageBlade.
For a quick overview of her abilities:
Divine Blessing heals up an ally and grants a movement speed bonus.
Intervention grants invulnerability for 2-3 seconds, which can completely alter the course of a team battle if used well. 
Lux is considered a support/mage. She can tear up teams with her chain of abilities, possesses a 2 unit root, AoE slow, and an amazing Ultimate.
Additionally, her main supporting ability is:
Prismatic Barrier shields an ally for damage. 
Morgana is just like Lux in that she is a support/mage. However, she is considered a better support for the shield she grants:
Black Shield is a very unique shield that blocks magic damage and any negative effects: all snares, silences, blinds, etc. This shield scales with 80% of her total ability power. It is a total carry protector and game changer skill.Additionally, Morgana has a single target root, a magic resistance debuff AoE DoT, and a powerful AoE stun.
I mean, is Sona good for help?
Sona is the queen of support in my opinion, closely followed by Soraka. All her abilities except for the ultimate give your teammates a buff and she can not be ignored damage wise.
Hymn of Valor is an aura granting a buff to damage and ability power. 
Aria of Perseverance is an aura that increases armor and magic resist to allies. On cast, it will heal the most wounded ally nearby. The Powerchord bonus decreases total damage output of the target by 20%
Song of Celerity gives a temporary movement speed buff to your allies, in addition to the aura which grants a fixed movement speed bonus! Can we count Soraka and why?
Soraka is one of the oldest support champions, and one of the most powerful ones. She has a single target heal plus armor buff and the ability to grant mana to an ally.
Astral Bleesing heals for a decent amount while granting 20-80.
Infuse grants mana to an ally. No other hero can boast an ability like this.
Wish is a global heal. The epitome of an incredible support heal.
Consecration, her passive, increases magic resistance for nearby allies by 16.Is Taric a tank, or a good support champion?
He can be both. Taric's base armor and health and armor/level and health/level increase are very high compared to all other support champs.
Taric can heal and has an Armor Aura, Damage Aura, and a Stun, which makes him a reliable support character. However, one of his downsides is being a melee character unlike many of the others mentioned.
Imbue, if casted on an ally, heals Taric and your ally. If casted on Taric, he heals himself an additional 40%.
Shatter is an aura that increases allies' armor by 10-30 and increases Taric's by double this amount!
Radiance heals Taric by an amount per second while granting an aura that increases attack damage by 15-45 (and double that on Taric). Make sure to use while taking down towers and in team fights!
Zilean is an amazing support champ with the unique ability to revive champions.
He is a great addition to a team because he posseses:
Time Warp is a single target Speed Buff/Debuff
Chronoshift revives a fallen enemy with scaling (200% of AP) restored HP and Mana. That's like fighting a 5.5 vs 5 :)
Heightened Learning, his amazing passive, gives all allies an 8% bonus to experience gained!As you can see, LoL offers you a wide variety of support champions to play.
Which champions are viable to play nowadays on LoL as support?
Depends completely, for instance:
Your team has an AP carry, AD Carry, a tank and a Beefy Meat Shield champ, what are you lacking? Since you already have an AP carry you can play a pure support champion like Taric, Janna, Soraka or Zilean.
Now if your team has already a Tank, an AD carry and a Jungler, your team will need some magic damage source, then playing Morgana, Lux or Sona will make the team composition solid.
If you want a current metagame opinion on which are the most played support champions, I would say Sona, Karma and Zilean.
Best Answer
ALL of the flash arrows on the picture you posted can be accomplished using the current flash, except two:
After tons of experimentation, here's what I came up with:
All the lines I've drawn are what I deem the "difficult" places where you can flash over. There are a lot more obvious places that I haven't put here that I thought were obvious or trivial, including many of the arrows on the picture you posted. There are also definitely some "difficult" lines I haven't drawn - if you find some crazy ones, let me know!
I tried to maximize the distance you travel in each location, unless for some reason it seems stupid that anyone would want to be flashing in that direction. However, I'm sure many of these aren't perfectly optimal. They're also not pixel perfect, but should be mostly accurate. If you can't seem to carry one out, feel free to message me and I will try give you suggestions. Also, if you want to suggest another spot, or just have questions in general, you may message me as well.
Hope this helps!