Hearing, Sight, Taste, Touch, and Smell. The five senses. Which would be the worst one for you to lose, and why?
I don't have a quick answer, but I'll still attempt this one.
Any would be crippling. Devastating. I try to be very aware of my surroundings - with him living in the back of my head, there isn't really a choice.
I suppose... hearing. Losing my sight would be terrible, but I could compensate to some degree. Humans can echolocate. There is... equipment made so that nonhumans who can't see in the visual light spectrum can still "read". True, there are ways to compensate for deafness as well, but from what I've seen they're cruder.