An American Derringer Model 1 can be seen in the armory belonging to the hunter Olivia Lowry (Audra Ricketts) in "Are You There, God? It's Me, Dean Winchester" (S04E02).
Colt Double Eagle
A Colt Double Eagle variant can be seen in the armory belonging to the hunter Olivia Lowry (Audra Ricketts) in "Are You There, God? It's Me, Dean Winchester" (S04E02). It is only seen at a distance so the exact model (fullsize, Commander or Officer) is hard to determine).
Heckler & Koch USP Match
The custom Heckler & Koch USP Match which originally appeared in Blade II is in the armory belonging to the hunter Olivia Lowry (Audra Ricketts) in "Are You There, God? It's Me, Dean Winchester" (S04E02).
Glock 17
Glock 17s appear in multiple episodes, often carried by law enforcement officers.
Beretta 92FS
A Beretta 92FS can briefly be seen on Sheriff Al Britton's (Jack Conley) desk in "Yellow Fever" (S04E06).
Revolvers
Taurus Judge
A Taurus Judge can be seen in the armory belonging to the hunter Olivia Lowry (Audra Ricketts) in "Are You There, God? It's Me, Dean Winchester" (S04E02).
Smith & Wesson Model 686
A Smith & Wesson Model 686 can be seen in the armory belonging to the hunter Olivia Lowry (Audra Ricketts) in "Are You There, God? It's Me, Dean Winchester" (S04E02).
"The Colt" (Colt Paterson 1836 cartridge conversion)
"The Colt" appears in the time travel episode "In The Beginning" (S04E03) and is in the possession of a young Daniel Elkins (Andy Nez) before being borrowed by Dean (Jensen Ackles).
"Back in 1835, when Halley's Comet was overhead, same night those men died at the Alamo, they say Samuel Colt made a gun. A special gun. He made it for a hunter. A man like us, only on horseback. Story goes, he made thirteen bullets. This hunter used the gun a half dozen times before he disappeared, the gun along with him... Somehow Daniel got his hands on it. They say... they say this gun can kill anything."
The pistol which is simply referred to as "The Colt" is a modified Colt Paterson 1836, first seen in Season 1. The actual gun appears to be built from a Pietta "Paterson Extra Deluxe" based on the engravings and silver inlay markings. The pistol is further modified with a cartridge conversion, by having a pentagram carved into each grip plate, and the barrel is engraved with "non timebo mala" which translates to "I will fear no evil" (a reference to Psalm 23).
Taurus Model 689
Several members of the Sheriff's Department in "Yellow Fever" (S04E06) carry Taurus Model 689 revolvers with blued finish a wood grips.
Shotguns
Side by Side Sawed Off Shotgun
Side by Side Sawed Off Shotguns are one of the most common weapons on the show, normally being used by the brothers whenever they are hunting ghosts. They are said to be loaded with rock salt shells due to the fact that spirits are repelled by salt.
Ithaca 37 (Sawed Off)
A sawn off Ithaca 37 is used by the brothers on several occasions, most commonly when hunting ghosts loaded with rock salt shells. It is also commonly used as a prop to hold open the lid of the weapons compartment in the trunk of the Impala.
A custom Ithaca 37 "Stakeout" with a chrome finish on the barrel and magazine tube and an MP5K style pump is used by the hunter Olivia Lowry (Audra Ricketts) in "Are You There, God? It's Me, Dean Winchester" (S04E02). The exact same weapon can also be seen in House of the Dead and Painkiller Jane.
Winchester Model 1300
A Winchester Model 1300 with a pistol grip can be seen on the body of a dead hunter in "Are You There, God? It's Me, Dean Winchester" (S04E02).
Coach Gun
A young Mary Winchester (Amy Gumenick) can be seen cleaning a Coach Gun in the time travel episode "In The Beginning" (S04E03).
Samuel Campbell (Mitch Pileggi) can be seen cleaning a stripped Side by Side Shotgun in the time travel episode "In The Beginning" (S04E03).
Winchester Model 1897
A young Daniel Elkins (Andy Nez) uses a Winchester Model 1897 in the time travel episode "In The Beginning" (S04E03).
Remington 870 (Pistol Grip)
At least two Remington 870 shotguns fitted with pistol grips, extended magazine tubes and Surefire fore-end lights can be seen in the trunk of the Impala.
Remington 870 (Wood Furniture)
Remington 870s with wood furniture appear in several episodes.
During "It's a Terrible Life" (S04E17) the Winchester brothers watch an instructional video on how to subdue ghosts produced by the Ghostfacers. During the video Harry Spangler (Travis Wester) can be seen with an airsoft replica of a Mossberg 500, identified by its shorter barrel with orange tip. It is portrayed as a real weapon but it is not clear whether is standing in for a real weapon, or whether the Ghostfacers are simply pretending that it is real.
Submachine Guns
Heckler & Koch MP5K
A Heckler & Koch MP5K can be seen in the armory belonging to the hunter Olivia Lowry (Audra Ricketts) in "Are You There, God? It's Me, Dean Winchester" (S04E02).
MAC-11
A MAC-11 cam be seen in the Impala's weapon compartment in "The Monster at the End of This Book" (S04E18).
Rifles
Colt M16A2
What appears to be an M16A2 can be seen in Bobby's safe room in "Are You There, God? It's Me, Dean Winchester" (S04E02). The scene is very dark and the rifle is only briefly seen so this ID is not certain, however the round A2 handguards are visible.
Winchester Model 1894
A magically animated giant teddy bear in "Wishful Thinking" (S04E08) uses a lever action rifle to attempt suicide. Although the rifle is never clearly seen, it appears to be the same Winchester Model 1894 which has been used in Season 2.