Pet peeves.

I was just talking with my friend (okay, ranting. There was some foaming on my part) about various common grammar errors that irk us, both in spoken and written English. IE e.g: Your/you're their/there/they're confusion or, my example, people using "less" when they should use "fewer".

So, basically, I'm curious about similar common mistakes that might be made in other languages. For you non-native English speakers: what are your language pet-peeves?

(Hell, English speakers are welcome to chime as well. I'm always up for a little linguistic frothing. ;) )

Edit: This has gone off the rails a bit, and I would like to apologize for my ignorance. I only posed the question out of idle curiousity, and I honestly didn't intend to make any sort of judgment or perscriptivist statement. In fact, I hadn't heard of perscriptivism before these threads (more proof of ignorance, I know). At least my eyes have been opened that much! The links provided have been very interesting.

Once again, I didn't mean to offend anyone. :x