An old one but good one: "paradigm." Remember in the 80s everything was "a new paradigm!" Everybody was using it, nobody could explain it! I still don't know what it means!
"It doesn't take a rocket scientist..." That's as bad as "Philadelphia Lawyer."
"Know what I mean?" Especially when said by rap singers at the *beginning* of a sentence.
Here are a few more: (video)
The words you love to hate - CNN.com