Hadouken is a Taunt done by the Pyro. This can be done with any of his secondary weapons, such as the Shotgun and the Flare Gun. The only secondary weapon that cannot do this taunt is the Scorch Shot, as this weapon does the Execution taunt. This taunt takes 3 seconds, and deals 500 damage (instant kill). This is a fairly short range taunt, when the pyro puts his hands back and thrusts them outward with palms facing outward with a burst of fire that is very short ranged. Anyone who survives this taunt (such as a Spy cloaked with the Dead Ringer is lit on fire. This taunt can mini-crit, dealing 675 damage, but like all taunts, cannot do a critical hit. This is best used on distracted enemies or around corners. This can pierce through multiple enemies, though this is unlikely to happen. Like most taunts, this can be done in Humiliation and Stalemate, but the achievement "OMGWTFBBQ" will not be earned if a kill is achieved.
Hadouken references the well-known move in the game Street Fighter.