My buddy and i went into a store that the ATF was doing a check on. The Agent was checking the on the shelf inventory with the books, it was obvious who he was.
My buddy was looking at one of those new, at the time, H&K pump shotguns with the carbon fiber look and noticed that it had a raised serial number, instead of the usual stamped in serial number most manufaturers use.
He said "Man, it'd be real easy to file off this serial number."
I about passed out. "Man, don't say stuff like that, that's the ATF over there!" (about 10 feet away)
He was joking, of course.
Funny stuff.