The bench press curl.
Wiki mentions it as a stand-alone exercise.
"[...]Yet another variation, the Bench Press Curl, is unique in that it requires two people to function properly in. One, lying on the bench (similar to bench press) lowers the weight eccentricly to 1/2 the ROM as seen in bench press, and the other trainee, standing over the bar, actively curls the bar upwards (essentially a barbell curl) as the other actively presses up."
(on the "Biceps Curl" page)
I wonder how many people will think this is an actual exercise.