The most balanced champions.

There are a lot of discussions on which champions need nerfs, buffs, or total reworks. What is never discussed is when riot has really hit the nail on the head as far as perfectly fair champions.

In my opinion Kennen is balanced phenomenally. When he gets ahead he can snowball and dominate, but still it remains possible to kill him, or escape. When he is behind he can still help the team with the utility from his ult and his other stun combo. He is strong but not too strong. His cool downs are perfect. His ult does the perfect amount of damage and the stun time isn't excessive. He can cc without being too suffocating. His item build path can vary dramatically.
All in all Riot has done an excellent job with Kennen.

Which other champions come to mind that are well balanced and fair in terms of their kit and their power numbers?

Another that comes to mind is Nautilus.