I'm not fluent in anything but english. I do know some french but it's _extremely_ rusty.
So far my go-to favorite is a french phrase: "enculeur de mouches"
Let's just say it means "nitpicking" but the literal translation is hilarious and not appropriate for general audiences.
Google translate almost gets it right.
Edit:
http://en.wiktionary.org/wiki/enculeur_de_mouchesI will not be held responsible if you are easily offended and click on that link. Text not safe for young eyes, and so on.