Things I can't imagine ever doing unless (and maybe even if) my life depended on it:

1) Eat my own (or anyone else's) placenta
2) LARP (live action role play)
3) Be a mortician
4) Try to create dinosaurs (a la Jurassic Park)
5)Be a forensic whatever-the-hell or cop or anything that might involve me having to deal with serial killers who wear people's skin as suits and the people they leave skinless. I just can't deal with gouged out eyeballs or any other type of mangling or mutilation.
6) Let ANYONE stick ANYTHING in my anus
7) Carry more than triplets to full term and birth them all. I'm sorry, NO. Judge me all you want but I'd rather choose a few to keep and abort the rest or never have any children again than carry like 8 babies. That's unnatural.
8) Marry some old ass dude for his money. I can't even think about what an 80 or 90 year old's dick and balls look like without spewing much less interact with said dude's package in the ways that I would probably have to.
9) Drown puppies or kittens. Sorry, old farmer dudes, I understand too many of them can be a serious issue and they will die of hunger eventually if they are overpopulated, but Jesus hates you for that and so do I.
10) I probably could not eat a person to keep myself alive. At least not raw. You know, like if you were trapped on top of a mountain or in a desert with absolutely no way to feed yourself. We're assuming I had nothing to do with them dying, just so that's said. I just don't think i could cut a slab off someone or just grab a leg and dig in, even if it meant i would starve to death.
11) have sex with an animal.  i shouldn't even have to explain this or say anything more about that.
12) perform surgery on myself
13) I would never have "19 Kids And Counting"
14) I would never pierce or tattoo my coslopus
15) I would never have a sex change

that's all I can think of off the top of my head. tell me a few things you would never do in the comments, if you feel like it.