A one-size-fits-all retort guaranteed to amuse or annoy.
For reasons that elude linguists, sociologists, and recipients alike, the phrase is sometimes held by its proponents to be the greatest comeback ever, and one to which no reply is possible.
Several studies have found a relationship between the humor value of "your face", the number of repetitions, and the average age of the audience. A commonly cited example gives the relationship as:
humor = 2^(n * (1 - abs(13 - age)))
This model predicts that for ages 12-14 "your face" never gets old. For age 13 its humor grows geometrically, hence a sequence of "your face" retorts may only end due to anoxia or exhaustion.
For everyone else "your face" just isn't funny.
Bob: dood, whut up.
Alice: your face is up.
Bob: that's lame.
Alice: your face is lame.
Bob: don't make me come over there.
Alice: don't make me come over your face.
Bob: that's whack.
Alice: your face is whack.