The OmniWrench is Ratchet's main weapon in the melee minigames and in general.
The OmniWrench usually looks like a normal wrench, which Ratchet used to fix his ship in Ratchet & Clank. It has a magnetic energy, which allows to collect bolts easily. In some games the OmniWrench changes. For example, Ratchet's OmniWrench 8000 became OmniWrench 10000 in Going Commando. Another Lombax named Alister Azimuth uses the Praedetorian OmniWrench, a different kind of OmniWrench. In A Crack in Time, they introduced the Kinetic Tether, which allows the wrench to move the platform to him or any necessary things.
In Sly Cooper: Thieves in Time, Sly's Cane can be changed into an OmniWrench through a process of a code. It changes as Ratchet's OmniWrench and a difference to money, turning them into bolts, the currency in the Ratchet & Clank universe.