Kennen simply is strong cause he is ranged. The problem when laning against Kennen aswell is, that your jungler cant really help you, cause Kennen can escape about 80% of the ganks.
One thing you can do is pick another ranged top against him (Vlad, Jayce, Nida), the problem here is that he either outscales them (nida, jayce) or beats them early (vlad).
You can also go with a very very tanky champ, preferebly a champ who has a shield (Malph, Udyr, Riven) and just ignore his early AA damage.
The third and last thing you can do is get a stronger late game champ (Jax, Irelia), go for 1 or 2 gp10 and just farm as much as you can. The good thing about these champs is, that they can beat a Kennen after 5 min alraedy if they get one succesfull gank of (or they get a kill from another lane).
What you have to remember is, that Kennens main advantage is his AA range and his snowballing cause of early dominance. Start cloth 5 if the enemy has a weak early jungler (Skarner, Mundo, WW), go for a Ninja Tabi if his AA are killing you really hard (even tho I wouldn't do that often, Mercs are simply better against his CC) and dont go for all the creeps early. If you have to take 3 or 4 Autoattacks, just to get 1 or 2 cs, its definitly not worth it. Try to passivly farm as much as possible and stay on more than 50% HP. As Irelia, you can sneak some CS with your Q till you get to lvl 6 and got 2 dorans or a phage, then you can beat him pretty hard. What you can do as a meele Bruiser is get some early MR and ninja tabi, and then just go for gp10 and late game.
EDIT: Most people know this, but they dont do it: Stay behind minions and dodge his Q. He will probably max Q, so if you manage to dodge it, you avoid 100-300 dmg early game.
Ruaans hurricane fires two bolt dealing 10 + 50% AD and apply on hit affect.
twitch ult gives bonus ad and changes your basic attack to a ranged penetrating attack.
So the only the bonus effect that twitch ult will have on ruaans is the increase of ad.
Twitch passive however is a on hit affect and should work.
EDIT
From Runaan's Hurricane wiki:
Twitch will still trigger the effect while Spray and Pray is active. The two missiles fired are unaffected by the ability, and remain single target, targeted missiles. As such, it is possible for an enemy to be damaged by both Twitch's pass-through attacks and this item.
The Ruaan's bolt range will always stay 300
Best Answer
Runaan's Hurricane is an extremely niche item and only useful on a small handful of champs.
In your case, I would never before have even thought about getting Runaan's on Kennen. It can work if you want it to but in my opinion you would be better off building more damage (assuming AP over AD here). Kennen just feels much more spell based than auto-attack based, which is why you should build more damage for spells.
As for Caitlyn, I feel she's one of those handful of champs that can really use this item well. As an ADC, of course she will be continuously auto-attacking the other team and getting her passive off every other shot would be a huge boost in damage. Even though it would be useful, it's not useful to the point where I would ever rush this item. It would probably be the third of fourth (including boots) after Infinity Edge, Blood Thirster and possibly a Phantom dancer as well.
As a side note here is some other champs I feel make use of Runaan's:
Runaan's can also work well with both Black Cleaver and Blade of the Ruined King since it will apply on-hit effects from both.