In Season 2's "Euphoria, Part 1", Baby Shoes uses a Ruger SP101 to shoot officer Joe Luria (Scott Michael Campbell) during the opening chase. Dr. Gregory House (Hugh Laurie) tests a theory by using a similar Ruger SP101 revolver with a spurred hammer to shoot an already deceased cancer victim in the head and putting the body in an MRI machine with destructive consequences.
Glock 17
In Season 2's "Euphoria, Part 1", Officer Joe Luria (Scott Michael Campbell) is seen drawing his Glock 17 on a suspect at the opening of the episode. In Season 5's "Last Resort", Jason (Željko Ivanek) uses this third-generation Glock to hold Dr. House (Hugh Laurie), "Thirteen" (Olivia Wilde) and several patients hostage.
Glock 21
The Glock 21 is seen used by Jack Moriarty (Elias Koteas) in Season 2's "No Reason".
Heckler & Koch USP Compact
In Season 5's "Simple Explanation", what appears to be a Heckler & Koch USP Compact is seen on the floor of a bedroom.
The M4A1 carbine is seen in the hands of Marine Sgt. John Kelley (Marc Blucas) in Season 3's "Top Secret" and carried by SWAT officers in Season 5's "Last Resort".
M16A2 Rifle
In Season 3's "Top Secret", House is seen holding an M16A2 rifle, fitted with an ACOG scope on the carry handle and a RIS handguard in place of the standard A2 handguards in a dream sequence.
In Season 7's "Bombshells", House is seen turning his cane into what appears to be a Mossberg 500 Cruiser shotgun fitted with a pistol grip and weaponlight in a dream sequence.
Other
Ramo RT-37
One of the prison guards in Season 8's "20 Vicodin" can be seen with a Ramo RT-37 during a riot.