The M274 Mule is an antagonist in Maximum Overdrive.
The M274 Mule is a small vehicle used by the U.S. Military, which saw use in military bases and the Vietnam War. This example has an M60 machine gun mounted in a pole from the center. Both the vehicle and machine gun operate differently but cooperate to gun down humans.
The M274 is first seen in a highway to the Dixie Boy truckstop along with a bulldozer. The bulldozer arrives first and rampages a small section of the truckstop. However, Bubba Hendershot, the Dixie Boy's owner, launches a rocket and destroys the bulldozer. Hendershot cheers his target's destruction, while the "mule" arrives and starts gunning the Dixie Boy, killing Hendershot in the process.
The Mule relentlessly shoots some of the surviving humans, killing three truck drivers and Wanda June the waitress. Wanda is killed after coming out of the Dixie Boy and repeatedly persuading the vehicles that humans produced them. After Wanda's death, the Mule beeps its horn in a Morse code sequence that only Deke Keller can recognize. He realizes the trucks and other vehicles demand fuel, and depends the humans to serve this need. The humans refuel the vehicles on the Dixie Boy, including those arriving in the truck stop.
Previously in the film the protagonist Bill Robinson speculates a fact if the vehicles are controlled by a comet. He wants the human survivors to move to an island free of the vehicles and dangerous inanimate objects. After the gas station is depleted of fuel, Bill decides to eliminate the Mule in order to safely free themselves out of the Dixie Boy. While talking to Andy the truck driver in the gas station, the M60 aims at Bill in intimidation. Bill leaves an activated grenade to the Mule and spins the M60 to protect themselves. The M60 is unable to shoot them, and both the Mule and the M60 are blown up by the grenade.