While strictly not negative, there are some that could imply you aren't playing your best or are playing the wrong class:
Nemesis - Get five revenge kills. - Means that you've had five people dominating you. However, this doesn't mean all at once, so it's not that negative.
Engineer - Death Metal - Pick up 10,000 waste metal from pieces of destroyed buildings. - To get this, a lot of your buildings (or your teammates/enemies buildings) have to be destroyed. Likely, this is because your sentry or dispenser got destroyed, and you're picking up the pieces for metal to build new ones.
Another class of achievements are ones where, to get them, you have to arguably play your class wrong:
Spy - Die Another Way - Kill a Sniper after your backstab breaks his Razorback. - Why are you backstabbing Snipers that have Razorbacks?
Pyro - Plan B - Kill 10 enemies while you're both underwater. - Pyro + Water = Bad
Heavy - Photostroika - Provide an enemy with a freezecam shot of you taunting while invulnerable. - AKA wasting the rest of the Uber.
Medic - Does It Hurt When I Do This? - Kill 50 Scouts with your syringe gun. - There are going to be some times when you're fighting Scouts, but if you're going out of your way to fight enemies, you're doing it wrong.
Medic - Peer Review - Kill 10 Medics with your bone saw. - See above, but add in the fact that you're not even using a distance weapon for this one. At least they cut back on the number of kills for this one.
Any taunting achievements that aren't taunt kill achievements. There is at least one per class.
The J.Axer's Dapper Topper, Amber's Rad as All Hell Hat and Uncle Sam are unique. There is only one of each, and they were awarded to the first, second and third place winners in the Propaganda Contest.
Some items were gifted in Self-Made quality to their creators. Where an item was credited to a single creator, the Self-Made version of that is the only one in that quality, although this isn't as truly unique as the item is more widely available in normal quality.
Other than the Top Notch, these are the only one-of-a-kind items in TF2.
Other rare items (fewer than 1,000 awarded) include:
Best Answer
Valve used to show some statistic of Team Fortress 2 map at this page. But unfortunately they have recently removed maps statistic in favor of leaderboards and achievements only.
Another good source of TF2 data stats is TF2Stats.net, but at the moment it shows only the popular maps and map saturation history. Could be that in future they will add more info.
UPDATE: I found a link to official
Valve's Team Fortress 2 Statsvia Google: here. It doesn't contain custom maps stats, but only official maps.