Counter

Counter is Marth and Roy's Down B move. Marth or Roy will strike a pose and a small, high-pitched sound will be heard. For about a second, any attack that Marth and Roy is struck with will be negated, and, if the attack is physical, a counterattack will be dealt to the attacker; Marth's Counter deals 7% damage regardless of the attack, while Roy's deals 1.5 times the original attack's damage. If the attack is a projectile (such as Samus' Missile), it will simply be deflected with the same animation as the reflection of a physical attack. Its worth noting explosive projectiles still explode and will still do damage (if a Samus Missile reaches its outside range, even deflecting it won't stop the explosion). If the attack is a smash attack, then the attacker will be knocked back at a 90 degree angle. If used in conjunction with Mr. Game and Watch's Oil Panic, it is the most powerful non-charged attack in Melee (if Oil Panic has absorbed the most possible damage, that is).

Ike also has this attack as his Down B move in Brawl. However the exact details of what it shares with Marth or Roy, and how it differs are not known at this time.