Before you read this, you should probably watch "Ew-in or Ew-out," as seen on Live with Kelly and Michael via YouTube. Ewan McGregor's answers are fine enough, but I couldn't resist posting my own here.
Brussels sprouts: I'm out. However, I don't think I've ever actually eaten a brussels sprout, so I don't know if I'd hate them or like them. Statistically, based on the fact that I pretty much don't like food in generally, I am going with not liking them. On the other hand, I love kale and spinach, but I'm just not willing to risk a bad flavor right now to find out about the sprouts.
Karaoke: I'm out. I'll play the music, but never will I be seen with a mic in my hand attempting to sing. And it's not even that I'm a bad vocalist: somebody told me I was terrible as a child, so now I'm against singing.
Peeing in the pool: I'm out. For the record, you should be too!
Re-gifting: I'm in. Why keep something I don't need if someone else could use it?
Manscaping: I'm in. Well, I am not a man, so I can't personally do any manscaping, but if I was a man, I'd totally manscape at least once.
Skinny dipping: I'm in, conditionally. I have nothing against being naked in water. However, if I'm going to skinny dip, I want to know for sure that nobody else is watching. So swimming naked, sure. Putting my wobbly bits on display for someone to watch? Not so much.
Dancing at weddings: I'm in. Well, as long as I have someone to dance with. Solo? No.
Honey Boo Boo: I'm OUT.
Plastic surgery: I'm out, mostly. For reconstruction or medically valid reasons, sure. For "improving," no.
Roller coasters: I'm out. I used to be in, but then I learned they make me sick and sort of give me panic attacks and generally make me want to die. I don't particularly enjoy that sensation.
Small dogs: I'm... neither. I don't really like dogs in general. However, I'm no more opposed to small ones than I am to large ones when viewed from a healthy distance. When they attack, small is preferable. When they protect, larger might be better.
Kissing dogs on the mouth: I'm OUT.
Baths: I'm in. Until the water gets cold about twenty seconds later. Then I'm out.
Speedos: I'm... out. I like the brand well enough, but there's not enough fabric to cover all the parts I like to keep covered, so no speedos for me.