So I had this idea for a combat system in a 2D platformer/fighter, think Raze or Super Smash Bros.
Each class has three weapons: a melee, a projectile, and a grab. I will use one of the classes, the Batter, for this example.
as the player fights, a special meter pops up for each weapon class and when at least two of those meters fill up, the player can use his/her Special Attack. The special attack is a combination of two weapons. The player can perform it by hitting R and selecting two weapons using the weapon buttons (Z for melee, X for projectile, C for grab) Using a special attack will drain both used weapon's energy (for example, Perfect Pitch would drain energy from Ball and Mitt) An item that kinda functions like a Smash Ball can appear during the fight, but you can turn it off. The item floats around and, when hit by the player, lets him use his totally-not-Final Smash, which combines all three weapons.