In Kingdom Hearts Final Mix, Slapshot is a combat ability that costs 1 AP to equip. It allows Sora to perform a wide uppercut slash instead of his default, slower thrust when near an opponent, and has a chance of dealing a Critical Hit.
In Kingdom Hearts II, Slapshot is an action ability that costs 2 AP to equip. It allows Sora to perform a quick uppercut slash when near an opponent. In Kingdom Hearts II Final Mix, Sora takes slightly longer to transition to other attacks after performing Slapshot. Its description is erroneously switched with that of Dodge Slash, but this was corrected in Kingdom Hearts II Final Mix.
Kingdom Hearts Final Mix
Kingdom Hearts II
Kingdom Hearts II Final Mix