Depends on the people I'm around; if they're pleasant, I'm a social butterfly. Obnoxious people piss me off, and I tend to speak my displeasure with them when I get to the point of not being able to stand them any longer. That's a rarity, though.
My biggest drawback is that I lose my mental filter. I had a somewhat slutty girl try to start up a conversation with me at a bar once, and I looked right at her and looked back at the bartender, who was getting me 2 beers. She looked at her friend and said, "That guy's a real *******." I looked at her in astonishment and said, "So not wanting to talk to a whore makes me an *******? All I wanted was to get a ****ing beer for me and my buddy." She walked off. The bartended sided with me, which made me feel justified.