I'm pretty sure someone's already mentioned the grossest things I can think of, but the weirdest is probably adult babies. Grownup people who get off on wearing diapers and crapping in them and sleeping in cribs. Not sure what all it has to do with sex really, but it's odd. Doesn't bother me really.

I used to be really way into the furry fandom and boy do they ever get imaginative. Cockvore-- wanting to get stuck into the urethra of a giant penis.

Again, I'm pretty non-judgemental when it comes to fetishes, especially silly imaginary ones, because I have some totally ridiculous imaginary ones myself (like I said before, I used to be into the furry fandom and still skirt the edges of it kinda) and honestly they don't hurt anyone.

The impression I get is that most of those people are just reaaaally big dorks. Like, some of them are just really hard to have a normal conversation with (something I value in a friendship). Childporn is bad, I think. Bestiality hurts animals; most of 'em have to be put to sleep after they've been fucked because it ruined their mind or killed their body. So, yeah, don't do bestiality. S'all I can think of.