Kennen is normally built as an AP damage engage champion, utilizing zhonyas combined with his R to do large amounts of damage and stun, but it leaves a few weaknesses.
1.) lethality champions can oneshot him or force him to burn his zhonyas, preventing him from ever getting an engage opportunity.
2.) he is very prone to dying from CC
3.) has less 1v1 potential for laning phase and is likely to recall multiple times early on.

With this build, starting out dorans shield and a health potion, kennen can easily stay in lane longer than most champions allowing him to get ahead on farm and levels. This gives kennen the potential to all in level 6 and kill his enemy laner on level 5. its recommended that you rush your mythic as fast as possible. Kennen recieves a huge 12 minute buff of SMF boots and +9 AR and MR and also +5% AR and MR from conditioning. At this moment he is likely the most powerful champion in the server assuming that he has achieved decent farm and an early kill.


Later Advice: if the enemy team is full AP, get MR boots instead of AR. but keep Abyssal Mask even against a mostly AD team, the passive will supply huge damage for your entire team.

I selected titanic hydra because it supplies additional AOE damage and sustain for kennen but your last item will be 100% situational. Make sure you use it to counter rather than stick to a single build. For instance into a lot of vamp and LS, i suggest Chemtech Purifier or Morello