Say, like, "well, I'm Noah's Ark, bitch! Me and my animals are gonna pair you off two-by-two, slice! Two-by-fuckin-two!"
Confusing people works surprisingly well.
The best come-back I can remember is when a female customer said "I need a bag" to a friend in a VERY condescending way while he was working the register. His reply was, "why? You ain't THAT ugly." I was there hanging out and my jaw dropped. The girl's face turned bright red and she grabbed her stuff, even though he tried to play it off as a joke. His father owned the store so he was safe.
Oddly, I had a run-in with a customer over a bag, as well. Same scenario expect it was a grumpy old man who was always rude to me, supposedly because he had a grudge against my parents. He did the same thing, acting like an asshole for no reason. I was sick of his attitude and lost my temper, so I said, "you can get a bag when you ask for one like a human being." He left in a huff and I never heard a word about it. He might have complained but I was really cool with the owner.
My favorite was a woman who, after I told her that her account was closed down, said, "You wanna see a bitch? Because I can be a bitch! I can be a bitch like you wouldn't believe!" and so on. I almost burst out laughing. I think I just told her she couldn't rent there and asked her to leave.
The worst I've ever lost my temper was when I was working at a skate shop. Punks would hang out there and rag on people. One guy, who was just a smart-ass in general, picked the wrong thing to say to me at the wrong time. I was usually pretty cool with it but he started talking trash about my father, who had recently died. I grabbed him by the shirt, pulled him halfway across the counter, pressed my forehead against his, and said, "don't say another goddamn word about my father." He got the message. His bud, who was standing beside him, gave me this mean look, until I said, "the fuck you looking at?" It was almost like something you'd see in a comedy, his eyes got big and he started shaking his head like crazy. I felt bad about it, though, and apologized later.
