(The prompts are all for Supernatural, but I think this list pretty much applies to any porn I may write.)
1. Non-con. (Sadly, a goooooood portion of the prompts are non-con or dub-con.)
2. Cross-generational incest, i.e. parent/child. (Actually, most incest is out, but this one is ALWAYS out.)
3. Really underage stuff. (Well, I'll write it if the younger one is like, 16, but not 12.)
4. RPF of any kind.
5. Stuff I deem 'Icky'.
It's the last one that really causes problems sometimes. But seriously, tennis balls? Forced enemas (hey, that's 1 and 5)? Mpreg-belly rubbing?
Your kink is not my kink... your kink is not my kink... @_@