The one that always bothered me is "same difference". It's like WTF? Is it the same or is it different?!You probably know what an oxymoron is - a pair of contradictory terms yoked together in a phrase such as "pretty ugly" and "awfully nice". Are you familiar with pleonasms? They're the opposite - a pair of redundant terms, like "new beginning" and "end result."
"Ear piercings while you wait"
Another peeve of mine is the use of non-words, like "supposably" or "irregardless".