Its a grenade with a stick handle that was used in WW2 by the Germans and Nazi's for exploding people in a very, "exciting" way...
For some weird reasons they also looked like potato mashers.
Jake: YOOOO, my friend let me borrow one of his Steilhandgrenate and I BLEW UP his car!
Jew Friend: WTF JAKE ARE YOU A NAZI OR SOMETHING-
German Stielhandgranate means "Steel Grenade" in German. Was the most popularized German grenades during WWII. It was equipped with a wooden handle and a metal 'cap' that containedexplosives. the handle was built to be thrown farther than the American and British grenades.