Not Updated For Current Season
Ok, so this is my first build I've ever created. I've been using it for a few weeks now, and it has been very successful so far. So here I'll take the time to explain a few things about the build, and how I particularly play Kennen using this build.
So to start off, this build really is rune and item dependent. Really, if you can't complete the entire build, I would not suggest using it. But with the correct runes/masteries this build can make you a heavy support and carry to your team, and earn you quite a few kills a long the way.
This is a mid build, with this build you have incredible creep farming abilities, while being able to pressure the enemy back to their tower constantly. With the items being high priced, you need the lane to yourself for the most money/kill ratio early game.
Summoner Abilities: I choose flash/ignite. While lightning rush is a great escape tactic, flash gives you the little extra boost to either get away from someone quickly, or get to someone quickly. I see this as a must have for Kennen. Ignite is great to mix with pressuring your lane partner to score some kills early on. With this build I've managed to score first blood within the first few minutes of the game consistently.
Items: As you can see there are 2 empty spots, fill these with whatever you like, some combination's that I have seen success with are Last Whisper, and another infinity edge. Boosting my crits up to 800+ per hit, I've used Madreds Bloodrazor to help nuke down high HP characters, but really. Look at who you are playing against, and plan accordingly these spots are up for you to customize.
Early Game: Start off with Boots and 2 HP pots and grab mid. With a couple crits and a decent attack speed already, you're going to be able to kill creeps pretty quickly, use shuriken for last hits, and farm up gold. If you're enemy is overextending, pressure him with normal attacks, and shuriken, keeping his HP down, and keeping him back. If he overextends, by level 3-4 you should be able to combo your skills with ignite and get an early/first kill. Remember Kennen is squishy though, so don't overextend too much, only go for kills you feel confident about, by level 6 comboing skills with your ultimate and ignite should easily earn you a kill. Try to stay in lane until you can atleast buy Berserkers Greaves, and a pick axe. By level 11 you should have your rageblade built, and can start moving around to other lanes and help earn some kills or assists, while pushing towers.
Mid Game: Mid game is tricky, because your skills aren't doing tons of damage by themselves, you should have phantom dancer by now, or at least be close. Your best bet here is going to be hopping lanes a lot, and going for team kills. Combo your skills with your team, go for stuns, and with your 8 stacks of rageblade and a bit of crit, you should be able to get some last hits. Just move about lanes, push towers with your team, and kill creeps as you can. Work towards that infinity egde, and try to avoid solo fights that you know you cant win.
Late Game: Now depending on how long your game goes, Infinity Edge may be the last item you end up being able to buy anyway. At level 18 and the full item build, you should be able to nuke down most enemies, stick to team fights and chase when you can, Kennens normal attacks and crits should be hitting anywhere from 300-600 depending the enemies armor, which is nice because if you have any big silencers on the other team, you're still hitting them for some high damage, if you're defending your attack speed mixed with crits will be plenty to nuke creeps down and keep them out of your base, and on the other hand if you're attacking, you should be able to bring out quite a few kills, and help nuke down towers/inhibitors and win.
For the games that seem to drag on forever, like I said. Plan your next item choices accordingly, and stick with your team for kills. If you play smart, you can bring out a very high KDR with this build, and be an essential carry to your team.
Anyway, I hope you like this build, I see a lot of people build Kennen as a mage, but I've seen plenty of success with building him as an attack speed/crit damage character as well. I'm sorry for not being extremely detailed in this build, but hey I'm up for criticism, and whatever anyone has to say for that matter, give it a try tell me what you guys think :] Thanks.