Here's some that come to mind:
Dough = money
Gung Ho = sure/obsessive? (My sister and her friends use this. They say, "Don't be so gung ho about it.")
Jinx = curse/bad luck (This word was a total hit back in elementary when we used to say "Personal jinx!" when you say the same word at the same time as someone else.)
Phat = cool? (I'm not sure...I'm not that ghetto.

)
Flash/Flashing = Mooning = showing your bare butt
There's more but my brain doesn't seem to be working. I don't use idioms very often...or I just can't identify them as idioms. Haha.