If this thread already exists, sorry, didn't see it.
Anyway, what are some pet peeves of yours?
I don't like it when people ask "What songs do can you play on guitar?" because I know a lot of songs on guitar and I never know if they actually know the songs I can play and when they don't know it just gets kinda awkward. Also, people who ignore the unspoken rule of "Don't play Smoke on the Water unless you know the whole song."