Someone talking on the speaker phone in their car. Most move their hands up and down and head side to side as if the person they are talking to is standing in front of them. Usually oblivious to anyone looking.
Dude #1: Hey, check out the guy next to us.
Dude #2: Wow, is he rocking out to Pantera or something?
Dude #1: No, he's just a "cell phone schizo", probably chatting with his ex.