A few of my favorites:
When I want your opinion Ill give it to you. (it takes them a minute, but when they get it, watch their face turn red.)
Who are you? (the ultimate insult)
Im trying to see things from your point of view, but I cant get my head that far up my ass. (great line... forget where I heard it. I used it on my mother when I was a wee lad... she didnt approve)
Are you a guy? (when you want a stripper to go away)
Peaches, I wouldnt take you to the hospital. (when an ugly girl asks you out)