Ya' don't say?

Ok so you've just come across an individual who has, somehow, worked your very last nerve. Either they've stepped on your toes at work, they've cut in front of you in the coffee line, they've flipped you off for some unknown reason in traffic, whatever. Maybe, in fact, you live with this person and they've said (or done) something that just has caught you briefly thinking some not-very-loving stuff.

Obviously, depending on who this person is (your boss, your sibling, your child, a total stranger) and the circumstances (face-to-face, e-mail communication, separate cars), your reaction will vary. For our purposes, let's use the "total stranger cutting in front of you in the coffee line" scenario.

Do you say anything at all? Do you politely bite your tongue and think "maybe they're on the way to the hospital for something awful"? Do you remind yourself "aw hell - big picture so I wait an extra 90 seconds"? Do you fake-cough, hoping they realize on their own what they've done so they can say "oh my - I'm so sorry. Are you in line?" and you can respond with something fabulously gracious like "I am, but it's fine. Please - go ahead" which you'll smile about later, when you realize that you took the high road AND did a good deed all in one.

On a related note, when you do have a confrontation like any of the things I've described above, how long does it take for you to come up with a response? Now typically, I go to humor, usually with a healthy dose of biting sarcasm and a complete lack of honest sincerity - something that says "yeah, you've pissed me off, but I either don't know you at all and don't care, or I know you well enough that this will pass in just a few minutes". It's a recipe that's worked for me for quite awhile now. Sadly, these witty, sarcastic, insincere responses tend to arrive about 40 minutes AFTER I require them. Sure, now and again I can pull one out at the moment it is needed - but more often than not, that's not how it goes. The fresh snappy comebacks take longer to bake.

Which is why I'm kinda waiting for someone to piss me off. I've got a wonderful lil' gem just waiting to be served. The bummer is that I'll have problems saying it with a straight face, 'cause I'll just be so glad to finally deliver it. So - until that happens - let's hear your favorite "snappy comeback" lines. (Feel free to include a description of when/where you used it, if you'd like.)