Limits...hm...
There aren't many for me...at least the common ones like rape and kiddy porn and whatnot, I don't have a problem with it and I've written them before. It's not real, so why be bothered? There's no place I won't go because I'm disgusted or anything. I don't write about...say BDSM not because it isn't my thing, but because I haven't experienced it and I wouldn't want to do it any wrong you know?
Some things I just can't do because I have OCD xD. Like scat, water sports, those types.
But everything else... I wouldn't want to not write something great or read something wonderful because it had a certain "kink" in it. I'd be denying myself. I'll try anything once.
There are of course things I don't do/read because I think it's dumb though...like the sex with a chicken thing xD. I am a bestiality fan but....chickens? Really? ...whatever floats your boat I say.
I'm also not of fan of AUs because I can't for the life of me ever keep a character in-character and...really I don't think any character in an AU could be in-character because they had to have grown up differently in that environment.
edit:
Oh yeah! Post 69 xD