i don't usually use comebacks, i prefer to just insult them, and wait. so while they're trying to tell me something to my face, i slow change my facial expression from a grin to a death stare to a mischievous smile. i also tend to do this also while in a regular conversation. people look up at me, stare blankly for a second or two, blink, and proceed to tell me i'm weird or start laughing or back off.
it's funny, because i started by insulting these two arrogant persons while i was working in a bar, so they tried their best comeback and i just did the face switch. one of them just looked at me and said, "you know, i have considered myself psychotic for years now, but i think finally, i've found someone that has bested me."
he then asked me whether i studied something, and upon telling him, he gave me his card and said i should call him about a job.