I used sugru to add better grip to my Xbox360 controller. Normally these would cost you upward to $20.00 a pack, and their grip still isn't all that great. Some people even go as far as to replace the analog sticks with the ones from PlayStation controllers.With sugru, my grip has never been better. Definitely recommended over those other grip alternatives.
Step 1: Get Some Sugru.
Step 2: Follow the Sugru Usage Instructions.
Don't want to mess it up now do we?
Step 3: Mould
Yay, you're done.