People who leave the keyboard sounds on instead of off on their phones drive me insane. Hearing "clickity click clack" at light speed is annoying, but the people who do it think you're being the annoying one when you call them out. It's the same with people who give someone a ringtone when they're always texting or calling them. Hearing the same 30 second ringtone multiple times in a row, and also less than 5 minutes grows annoying.

Mute. Your. Phones.