Mega Man X6/Parts

In this game, there are five types of Parts. Life / Energy Parts increase the maximum size of your character's life or weapon energy meter. These are equipped immediately and can't be unequipped or transferred; they affect only the character who picked them up. Normal Parts can be used by either character, and must be equipped to take effect. X's Parts work just like Normal Parts, except only X can equip them. Zero's Parts, similarly, are only usable by Zero. Finally, Limited Parts can be used by either character, but have only a temporary effect and must be activated manually from the pause menu.

You obtain Parts by rescuing the 128 Reploids that are scattered around the eight main stages. Each part is held by one specific Reploid, who will give it to you if you rescue him/her. To rescue one, simply touch him/her. But you cannot equip or unequip Parts during a stage, you must choose and equip your Parts before starting a stage.

You can only have a limited number of Parts equipped at once. The number of Parts you can equip depends on your Hunter Rank, which is determined by the number of Souls you've collected. The more Nightmare Souls you collect, the more Parts you can equip. However, this limitation does not apply to Life / Energy Parts, you can have as many of those equipped as you want.