Tattoos don't really bother me, as long as they're not excessive. Piercings, on the other hand -- gah! Earrings I don't care about, but others, especially facial piercings, just look garish and ugly to me. I find it especially unfortunate if the person has an otherwise attractive face.
Smokers; now, I know there are plenty of smokers who are decent people --hell, I live with a couple of guys who fit that description-- but knowing someone smokes still makes me think less of them. I mean, they're knowingly inhaling toxic, carcinogenic substances -- where's their common sense? I just don't get it. Plus, I generally just think it's a disgusting habit.
Oh, and since a few people have brought it up, I don't trust animals either. Sure, some can be trained, but ultimately, they don't really have a sense of right or wrong. They're relying on instinct over intelligence, and that makes me reluctant to have one as a pet. Plus, many are just bothersome and demanding creatures that are constant irritations. To be completely frank, I only like animals when they're crispy and in my stomach.