Weapons are a big part in any Ratchet & Clank game, and All 4 One has plenty of variety in its selection. Instead of weapons powering up as you use it, weapons in All 4 One have purchasable upgrades of three varieties. These are Ammo, Power and Elite, which simply costs bolts; you must purchase the first two before the Elite upgrade becomes available.
To emphasize the multiplayer/cooperative nature of the game, weapons will do more damage or add special effects if used by more than one person. Note that if playing alone, the AI will use the same weapon as you do. For example, if all four players use the Combuster on a single enemy, a circile will begin to expand outward and once it reaches a certain size, it will "explode" and grant a damage bonus.