In Season 2's "Euphoria, Part 1", Baby Shoes uses a Ruger SP101 to shoot officer Joe Luria (Scott Michael Campbell) in the episode's open. 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 was used by Jack Moriarty (Elias Koteas) in Season 2's "No Reason".
M4A1 Carbine
The M4A1 carbine is seen in the hands of a Marine officer 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.