Well I have a few musical dislikes...
Rap - I don't like it, because it seems redundant to me. All the songs are of similar subject, and it sounds all very similar. A beat made from a horrible electronic drum emulator, and then someone rhyming over it, and usually using non-English(mostly non-sense) words.
Pop - It's too happy. Not that I don't like happy music. Also, I am very picky when it comes to vocal styles, and a lot of it is whiny. Again, I don't like having a lot of electronic or simulated instruments in music, for me it takes away the purpose of making music. It makes it, for me, unnatural and fake sounding, which to me is unpleasant.
Country - I can't stand southern accents... haha I just can't. Plus, the twangy country guitar sound isn't something that works for me.
Scene/Emo/Whatever-you-want-to-call-it - It's very whiny, which I really can't stand.