I may have mentioned once or twice that I hate fey. They’re nothing more than an annoyance. As for abyssal creatures, my favorite is probably the glabrezu demon. There’s just something about a half demon, half crab that can cast spells that is oddly amusing and appealing at the same time.
Another part of it is the experience that my bard turned cleric had on Occipitus during the Shackled City adventure path. We had some fun interactions with a glabrezu, among other demons.