Instant, G (1)

Cast Berserk only before the combat damage step.
Target creature gains trample and gets +X/+0 until end of turn, where X is its power. At the beginning of the next end step, destroy that creature if it attacked this turn.
Illus. Dan Frazier

10/4/2004: If the permanent stops being a creature before the end of the turn, it is still destroyed.
Legal in Vintage (Type 1)
Legal in Legacy (Type 1.5)
Legal in Classic (MTGO)
Legal in Commander