I've been known to dab my controllers with water after people that I deem gross have touched them.
This is the answer.
clorox wipe that shit man
i open up my controllers and clean all that gunk out from inbetween the two pieces.
I try to keep my own hands clean too, washing them if I've been out or just ate something.
And that's why I'm glad I got the special edition Black Wii. Came with two "grip covers" and two wii motion plus things.
Wiimotes are the worst... The god damn rift that runs along the side of the controller gets really dirty all the time. Sure, all you need is a Q-tip to clean it out, but it has to be done every few sessions...
but i still find my self wiping off the other controllers with Clorox wipes and a damp rag after people leave...