The Grinder is a small red bumper car that belongs to the Daredevils, but only appears in the boss mission in lava falls delivering ammo to Woody in his turret. It is unlocked by collecting the parts and blueprint for it in Lava Falls.
The Grinder is base on a weaponized bumper car. Realistically these wouldn't be able to operate properly outside the carnival ride. It has a gun attached to it's conductor rod. When driven it's engine sounds like an electric motor.
Being a novelty vehicle, the Grinder really isn't practical to use for anything, as it has poor stats, it can however, be fun to drive around in.