My biggest pet peeve is to be interrupted, especially when I'm talking or explaining something. I've walked out of many businesses and hung up on many businesses for that reason and even hung up on friends for that reason. It's downright rude.

My second biggest pet peeve would be obnoxious chewing, smacking lips, or pets licking themselves...that sound is beyond nails on a chalkboard...it makes me go ape shhh...