Erik: Honestly Charles, I don't know how you survived living in such hardship.
In the original X-Men, he just can't help but point out Scott's at-times apparent stupidity. Such as when they were all trapped and bound by him within the Statue of Liberty.
Cyclops: Storm, fry him! Magneto: Oh yes. A bolt of lightning into a huge copper conductor. I thought you lived at a school.
He also really enjoys mocking Wolverine in general.
Toad in X-Men. "Werent you meant to bring someone back with you?"
Professor Charles Xavier.
Professor X: Logan, my tolerance for your smoking in the mansion notwithstanding, continue smoking that in here, and you'll spend the rest of your days under the belief that you're a six-year-old girl. Logan: You'd do that? Professor X: I'd have Jean braid your hair.
Wade Wilson was already a wisecracker long before he ever became Deadpool; for example, he can't stop snarking at Ajax and Angel Dust even when they're in the middle of performing horrific experiments/torture on him. He sheds the "Deadpan" half a bit after donning the red suit, but his actual snark goes Up to Eleven, with the movie itself not being safe from his remarks.
Vanessa's ability to match Wade snark-for-snark is part of why they fall in love so quickly.
Negasonic Teenage Warhead possibly fits the trope even more so than Deadpool; at one point, the latter challenges her to make a comment that isn't mean and snarky.
Deadpool: "Oh look, I'm a teenage girl! I'd rather be anywhere than here. I'm all about long, sullen silences, followed by mean comments, followed by more silence." So what's it gonna be, huh? Long sullen silence, or mean comment? Go on. NTW: ...You've got me in a box here.
Even Weasel, who is such a wimp in the comics, gets in on the action, with the string of comparisons to Wade's scarred face and the constant insults directed at Ajax and Angel Dust even as they shake him down at his own bar for information on Deadpool.
(as they are leaving) You sure you don't want any clothes that aren't monochromatic? Have fun at your midnight showing of Blade II.