[Mr Cat Dog]

Smell. Hands down. I honestly wouldn't know how I'd cope without sight or hearing, so those two are off the table. I can't imagine anything good from coming from a lack of touch, so that one's off. And I love food too much to lose my sense of taste. Obviously taste and smell are connected, so I hope losing one wouldn't lose the other... but it's the price I'm willing to pay in this hypothetical scenario.