Water. Something about swimming absolutely terrifies me, which sucks because I do actually like being in the water. I used to be a good swimmer; but this all changed around the time I was 13. Now I can't go near a swimming pool or the ocean, or I get covered in shivers. However, showering is fine.
I dont have any debilitating phobias that I am aware of. I dislike heights, but I can manage if there are restrictions in place. I do gag at the sight, however, of babies puking in adults mouths (just youtube it with 'AFV' in there somewhere). Its a disgusting sight indeed.