The Heckler & Koch USP is a handgun in several variants, seen in the first Underworld film.
In Underworld, Selene is seen firing off a Heckler & Koch USP Compact at a statue. It isn't long before Kahn enters with a Heckler & Koch USP MATCH loaded with the first batch of Silver Nitrate Ammunition.
Later on, Kraven is seen wielding the weapon and shooting Lucian with the USP MATCH several times. He also shoots Michael Corvin with it and after being stopped by an injured Lucian, Kraven killed the ancient Lycan with the Silver Nitrate Ammo.