Equipped creature has ", Unattach Razor Boomerang: It deals 1 damage to any target. Return Razor Boomerang to its owner's hand."
3/1/2010 The source of the damage is Razor Boomerang, not the equipped creature. However, the equipped creature’s ability is what targets the permanent or player. If Razor Boomerang is equipped to a red creature, for example, the ability couldn’t target a creature with protection from red. It could target a creature with protection from artifacts, but all the damage would be prevented.
3/1/2010 Unattaching Razor Boomerang is a cost to activate the equipped creature’s ability.
3/1/2010 If Razor Boomerang is no longer on the battlefield by time the equipped creature’s ability resolves, it’s not returned to its owner’s hand. The rest of the ability resolves as normal, so Razor Boomerang will still deal damage to the targeted creature.
3/1/2010 If the targeted creature is an illegal target by the time the equipped creature’s ability resolves, the entire ability doesn’t resolve. Razor Boomerang remains on the battlefield unattached.