Mare's leg 

Originally used to refer to a cut-down/shortened lever-action rifle without a stock. Modern usage indicates any lever-action weapon built, or altered to be more portable/concealable and also without a stock with witch to put up against your shoulder. Legally considered a handgun when manufactured as such.

He almost got zombie kill of the week with his mare's leg.

Mare's leg by M3D13V4L October 15, 2011