I knew a guy everyone called whore bait.
There’s always this one from Buffy the Vampire Slayer: “Your mouth is moving… Sounds are coming out of it… This is never good.”
Or this one, same source: “So very funny - any moment I’m sure to laugh.”
Then there’s the times I’ve insulted people accidentally. For example - I was pestering a friend of mine to tell me interesting stories about her life. During the conversation, held at walking speed, we bumped into a mutual friend. Exasperatedly, Friend 1 pointed at Friend 2 and said, “Ask HIM for stories! I’m sure he has loads!” In confusion, I replied, “But I want your stories; you’re pretty!”
Luckily, Friend 2 took no offence.
Mrs. Call was reading this thread over my shoulder. It reminded her of an accidental insult she lobbed at a, shall we say “portly” friend of hers. Her friend was eating and had a bit of food on her face. Trying to be helpful, without thinking, Mrs. Call said, “You have food on one of your chins.”
[moment of silence]
Both had a good laugh about it.
Not mine, but my favorite: Dorothy Parker and Clare Booth Luce were entering a room together, and Luce stopped to let Parker pass, saying, “Age before beauty.”
Parker walked on, saying, “Pearls before swine.”
Okay, it may be apocryphal, but it’s still the best snappy comeback ever.
I have a friend who never does any type of housework and constantly complains that his wife “nags” him to clean up (after himself–the nerve) and one time I called him and he said he was vacuuming and I said, “doesn’t that hurt your penis?” I meant it to mean that he thinks having a penis means never vacuuming, but he thought I meant that the only reason he would have the vacuum cleaner out would be to put his dick in it when nobody was looking. So I got unearned zing out of it. That’s why it’s my zingiest. It doesn’t work as well for other applications even though I’ve used it many times since. “I’m going to get photocopies.” “Okay, don’t hurt your penis.” It doesn’t work, but I still say it.
My ex bf and I were fighting a couple weeks ago. He’s in the USMC (this is slightly relevent). I called him and after a minute of yelling at him, I realized I was on speakerphone.
He says, “Well I don’t know why we are fighting about our NON EXISTANT RELATIONSHIP!”
His buddies, “Ooooooooooooh!!! You told her! Ohhhhh!”
Me (very calmly): “Sweetheart, why are you showing off for your Marine buddies? You don’t want to have to be the bottom again tonight?”
Buddies: “Ooo-- wait…dude…not cool…”
Suddenly I was off of speakerphone and he whispered, “Sweetie, I’m sorry, I’ll call you back later.”
…It was a proud moment for me.
“You flocculating knobgobbler.”
I love this method. I use it too, with slightly different phrases. I even use it on obnoxious drivers. The slow sad “you poor dumb fool” headshake seems to enrage people far more than getting flipped off.
Sadly, I haven’t reached the level of maturity to actually MEAN it. I enjoy the rage this sort of “zinger” brings on far too much. 
I’m still waiting for the perfect opportunity to trot out my fave line from “What Planet Are You From?”:
You appear to be intelligent, but when you open your mouth, the effect is ruined.
I hope I don’t laugh… it was perfect how Ben Kingsley delivered the line with a totally straight face :wally
I had an English teacher once who explained profanity is actually pretty lame and doesn’t do much. Calling someone a fucker is easy but insults hurt much more when there’s effort behind them.
I realize this is not your original meaning at all, but if in the right context and said in a certain way I think that quote might possibly be one of the most painful phrases to say to someone. Ouch.
I recall ever being in a situation where a zinger of an insult was called for. I did tell a planner who thinks everything in our zoning ordinance is open to interpretation that I was impressed at his committment to cutting edge French thought with his post-modernist deconstruction of the text.
But I did have a great comeback the other day that I wanted to share. I stopped at a business to tell them that their banner was illegal and it had to come down. The woman said, “We had another banner up for six months!”
I said, “And you should be glad I gave you such a break.”
It wasn’t funny, but it stopped all protest and got the banner down the next day.
Working tech support once, and our boss called a meeting where he explained that he’d taken a job with another company and would be leaving in two weeks. We were all pretty down, since he was a way cool boss, but the department jerk (it’s a rule, right? All departments have a minimum allotment of one jerk.), who was a complete and total braggart started going on about how he was going to be boss next, and he’d crack the whip over our heads, etcetera.
Now, I had the reputation of being the department mother hen - I brought cupcakes, gave shoulder rubs, checked on people, did a lot of training. I was rarely mean. However, I couldn’t stand the jerk. So, I said, “Jerk, the day they make you boss is the day I open my veins over my trashcan with a rusty X-Acto knife.”
There was a long moment of silence, and another tech said, “can I borrow it when you’re done?”
It was lovely in that the jerk shut up for a few hours, my boss turned red laughing silently, and my coworkers were well pleased with me.
The best zinger I ever heard was from Bette Davis. Davis, upon hearing the news of her arch-nemesis Crawford’s death said, “You should never say bad things about the dead, you should only say good… Joan Crawford is dead. Good!”
I’ve been wearing below-the-knee gangbanger type shorts for like 10 years now. Way back when, I used to get a lot of flack from people about them. One day, a guy at work, Joe, confronted me with 2 of his buddies and asked me what the deal was…
Joe: I mean, are afraid it’s gonna rain? Is that why you wear those “floods”?
Me: No, Joe. I just like the extra room so I don’t get all bound up while I’m working.
Joe: Well, hell. I’ve never had to wear anything like that and I don’t have any problems.
Me: I’ll bet you don’t, Joe. (Walk away and cue the laughter from his buddies…)
I also like this line from an old Emo Phillips bit, where he is relaying a story about hitting on a woman (I’ll paraphrase)
Her: I wouldn’t go out with you if you were the last man left on Earth!
Emo: Lady, if I was the last man left on Earth, you wouldn’t even be allowed in line!
Here is a favorite from a friend of mine:
Stupid person does or says something really stupid.
Response: “I’m sure that whatever is wrong with you has a long, Latin sounding name.”
Sometimes zingers come in two parts: the setup and the close-out.
One time a co-worker of mine started (for no apparent reason) to whistle a familiar tune in his cubicle. It was “If I Only Had A Brain” from The Wizard of Oz.
So I piped up and said, “You know, it’s not a good career move to be whistling ‘If I Only Had A Brain’ at the office.”
Laughs all around, and he stopped whistling. But I was ready and waiting for the moment which came about 2 minutes later from the whistler: “Maybe I was really whistling the Tin Man’s song, ‘If I Only Had A Heart’!”
To which I said almost before he finished his sentence: “Not if it took you that long to say it!”
You are SO going to hell for that.
At work, the topic of grapefruits had come up for some reason, and one of the guys said he had balls the size of grapefruits. I came back with, ‘We’re talking about grapefruits, not grape seeds.’ Had the entire department in laughter, even the guy I zinged.
Did your mother have any kids that lived? Always liked that one.
Best comeback ever:
A woman approached Churchill: “Sir, if you were my husband, I’d give you poison.”
“Madam, if I was your husband, I’d take it!”
my friends and i were sitting around around our dorm room with this one kid who was kind of a hanger on that we didn’t really like. He had the sort of personality that could get my temper up really easily. So we were listening to Rammstein and he kept making fun of it by pointing out what the lyrics meant. i told him to stop
he continued
my friend told him to stop
he continued
I snapped
"You know from someone whom i’m sure has heard the words No and Stop as often as you have i would have thought you’d learn what they meant by now.
Also if you want to go for show stopping profanity
You cum crusted cock-mittin of a thunder cunt