Invented circa 1992 by Allen Gross. It was intended to be a more humane rattrap. Instead of killing the rats, it flung them up to 50 feet into a cage or bucket. The dazed, but still living, rodents could then be either turned over to authorities or released into the wild. Noted Gross, “I didn’t want the (rodents) squashed or turned into meatloaf.”
Santa Rosa Press Democrat - Feb 14, 1992
Staunton News Leader - Feb 14, 1992
Turns out this wasn't the first rat-flinging trap to be invented. Back in 1912, a similar device debuted, also called the Ratapult. Though it wasn't intended to be in any way humane:
A metal arm, operated by a powerful spiral spring, is released, and, passing through a slot in the cavelike compartment in the manner of a catapult, it strikes the unfortunate rodent with a blow of sufficient force to break every bone in its body and hurl the carcass at least fifteen feet away from the trap, far enough away so other rats will not be warned against the trap.
Vergennes Orwell Citizen - Jan 9, 1913