Dredg. I dig 'em a bit musically, but the vocals have this sort of angsty Californian thing going on, makes me feel uncomfortable listening to it. Not that there's anything wrong with the Californian accent, but a lot of bands from around there have these horrible pop-punky vocalists. Dredg's is among the most irritating.
Also! Fairly minor one, but Tim Donahue's "Madmen & Sinners" is transformed from a fairly nifty sideproject with some damn catchy songs, into a nigh-on unlistenable sideproject with some damn catchy songs by its hideously muddy production.
More controversially... Spock's Beard are one of those bands that I kind of like, and I can really dig bits of, but then they go and throw in something cringey. Songs like The Ballet of the Impact, June, Strange World, NWC, At the End of the Day, The Great Nothing are all brilliant, but then you listen to, say, the intro to In the Mouth of Madness (*bloop-bloop-bloop-bloop bleep!* "hey there Mr. Fancypants!") and it's all a bit jarring. I do get their sense of humour, to an extent, but I don't always find it funny. Even calling the band Spock's Beard, it's less "hahahaha!" funny and more "...no, really, try again."
They're like watching your dad dance at a wedding. Equal parts brilliant and embarrassing, and although there IS a sort of wonderful joie de vivre to the whole sordid display that you've gotta respect, and yet if anyone asks you'll still insist you've never met him before in your life EVER and if you think otherwise you're lying to be popular which probably means you have had a rubbish upbringing, and it's probably your dad so ha!