I really cannot stand it when people use an ampersand (&) for the word "and."
"I went to the mall & we bought shoes & clothes & saw an old lady with purple hair & big glasses & blahblahblah."
My god, it infuriates me. I also hate people using a commercial at for the word at, too.
"I'm going to be @ the stadium @ 4:00.."
Though, it bothers me less so than the former.