Merseytravel 142 is a given - weirdly, I actually like the bus seats and ATW 2+2s. (I like any old bus seats as they're much better than seven year old Enviro 400s).
150/1, because the seats and windows don't line up and the squabs break now and then.
185. No padding at all, and besides - they're always all reserved!
Anything with the narrow high-back seats, usually 3+2, that plague everything from Southern's 455/6 to 90mph spec 350s.
390s and Voyagers - again, obvious.
I do like 175s, Northern 158s, and anything of that ilk with those wonderful 1990s wide seats. Presumably I'd like Mk3s and 180s, but I've never been on either (yet). TPE's 170s aren't too bad, and Northern 156s have acceptable seats for the journeys they make, too.