What grammatical errors really piss you off?

[paperjam]

"I could care less" - I tried explaining to a co-worker that she means she couldn't care less, but she didn't care.

"Literally" - used for exaggeration, but rarely ever used to mean literally. I am watching past Super Bowl highlights now - and the narrator just said "he was literally facing a Catch 22" - really, like a copy of the famous novel was on the defensive line?

And this isn't grammatical, rather spelling, but definately...I would estimate 30-40% of Americans do not know how to correctly spell definitely.

What grammatical errors really piss you off?