For me, it would have to be chimpanzees. I don't know what it is about them but I've never liked them. There's something really sinister and bad about them.
Eels! Ever since I found a dead one in the lake nearby I've held them in contempt as my least favourite animal. Nasty/vicuous looking teeth, bad smell, slimy to the touch. Disgusting.
Squid and octopus, if one even comes on the TV it makes me shudder and feel seriously sick, there was one in a film i watched at the cinema once and i screamed, pretty embarrassing to say the least!
For me, the one that creeps me out is the Surinam Toad. Basically, it incubates its eggs on its back, then the baby toads literally pop out of its back like pimples. shudders lol