Arthur Ketch can be seen packing a case of weapons in 12.02 Mamma Mia, as he prepares to head to the United States. In addition to the guns, he also has an assortment of knives and other blades.
Ketch is cleaning his Heckler & Koch USP .45 with a nickle plated slide, before securing it in the case.
Ketch has at least three revolvers, makes and models yet to be identified.
Ketch also has what appears to be a Springfield 1911 .45 in the case. The same, or similar, to the gun Dean uses.
Heckler & Koch USP .45
Throughout Season 12, Ketch uses multiple guns. His main firearm however, appears to be the nickle plated H&K USP .45 calibre. He is seen using it multiple times, including with a silencer.
Ketch has attached a silencer to his nickle plated H&K USP .45.
Heckler & Koch USP .45 Expert
The gun Ketch uses during the fire fight in the Bunker is slightly different than his nickle plated USP. It appears to be an H&K USP .45 Expert.
When Ketch gets into a fist fight with Dean in 12.22 Who We Are, he pulls a small, concealed gun on Dean after he begins to lose the fight. It appears to be a Walther PPK, the gun of James Bond.
Ketch pulls a super compact gun, possibly a Walther PPK, on Dean