A crack that is wise. No, not the drug.
(most effective if a straight face is kept)
Bill: "Hey guys i got some sweet new k-swiss"
John: " yea dude, those K-swiss you have there are totally sweet."
Bill: "hey thanks!"
10 minutes later...
Bill: "hey dude was that a wisecrack??"
John: Not at all man. Wisecrack? I dont even know what that is.