Instant, 1BR (3)
Uncommon
Cast Delirium only during an opponent's turn.
Tap target creature that player controls. That creature deals damage equal to its power to the player. Prevent all combat damage that would be dealt to and dealt by the creature this turn.
Illus. Terese Nielsen

10/4/2004: Tapping the creature is part of the effect and not the cost, therefore you can cast this targeting a tapped creature.
Legal in Vintage (Type 1)
Legal in Legacy (Type 1.5)
Legal in Classic (MTGO)
Legal in Commander