Doppleganger (3.5e Maneuver)

The enemy is seeing double, as you hit them once, then your shadow hits them again!

You duplicate yourself as a shadow which repeats all the actions you take until the end of your turn. All the duplicated actions are only 50% effective, so an attack with a weapon deals 50% damage, and an effect which doesn't involve numerical changes has a 50% chance of working at all. The shadow isn't a creature and can't be attacked. The shadow provides no bonuses on miss chances, it is clearly unreal.