Not a lot of mean things, and, after looking at some of the others posted, some seem quite a bit more mild. Some of these included:
Me being "big," meant in the fat way. (Sure, I'm a big guy, but I'm not fat.)
Being crazy for my (clearly non-crazy) views on politics, economics, philosophy, belief in God, education, etc.
Once after making a humorous observation, a girl said with the utmost seriousness "That's not funny, and you're not funny at all." (Oddly, my guy friends find my dark, Pythonesque/British, and dry sense of humour great.)
Not having the "right" aims in life. I live my life as I see fit and love: endless intellectual discovery and thinking. Though I realize that finding a job and making money are important, they aren't my life's purpose.
I take my special interests too seriously.
Being boring and monotone.
Having "weird" taste in music and films.
Reading too many books.
Of these, I think the things that have stung the most have been mean things related to my stuttering. For example, I need to get it "cured," I'll never get a girlfriend due to it, no girl would take any interest in me, die a virgin, etc.