This is my first guide, so I really am hoping this turns out alright and useable for everyone. I want to first start by letting everyone know that Kennen is a very straight forward champ to play; however, he is not always a run-in-guns-blazing champ. He will develop into that if you play him right, but at first he is a harass and timed nuke champ to start. You have to play fairly defensive with him and always remember Turret Diving with him has a 60% mortality rate for you (this statistic is not including whether or not you get the kill you were after, so dive at your own risk.) I honestly mid with him 8 out of 10 times but I will play him other lanes as well with pretty good results there too, but much slower on building pace unless you earning your Mejai's stacks early. Play on, Rush hard, and Enjoy.

This build with him is pretty straight forward. Tome to Pick, Tome to Mejai's, Needlessly Large Rod then Blasting Wand to Rabbadon's, Blasting Wand then Tome to Void Staff, Blasting Wand to Rylai's, then Finish Deathfire for the full build.

Mejai's is a big deal of this build one for the great AP boost 20 stacks will net you plus the cooldown reduction is a massive help for the pesky champs who can outrun you. (Lighning Rush usually fixes that pretty quick. Lol)

Variations by Situation

Tough Enemy- If your having problems chewing through someone earlier or mid-game, there is a very simple solution. Build Void Staff before Rabbadon's. This will make your game run much smoother usually. The AP boost quicker than your Rabbon's plus an earlier Magic Pen. usually will help chew through some Tanky Champ when their builds are starting to come together (i.e. Nunu or Cho'gath.)

Bad game or Low Kill Game- This part is easy to fix. Mejai's is a big deal for the core of this build if your having a bad game, change it up a little bit. A couple of options are Morello's Tome to replace Mejai's or Zhonya's Hour Glass after you build Rabbadon's (in this instance build Void staff before Rabbadon's for a quicker boost and earlier Magic Pen.)

Honestly, there are plenty to recommend.

I have two combos I usually use.

Spell set 1- Teleport, Ignite
Spell set 2- Flash, Surge

Any variation would probably work just as well. Play with this and figure out your own combo to suite your play style.

To this day I've never really messed with Runes to be honest. So I would like to get comments and feedback to maybe add rune help to this. I just don't really know runes enough to say what is best or not.

Pros

-You turn into a champ kill and farming machine.
-All said and done with the build with all stacks there you end up with roughly upper 700's
or low 800's for AP. Definitely Nuke potential.
-Play your skills and summoner spells right and you can be anywhere and kill anyone.

Cons
-Must play very defensive early game.
-In a lot of cases your still pretty squishy.
-If you slow down, your probably gonna die.

In conclusion, he's a fun and at times, hilarious character to play. Just play hard, kill everything, and wait for the other team to hunt your down. Lol