What are the revolvers from Trigun called? Do the revolvers that Vash and Knives carry in Trigun have names? Is there anything they are called individually?
The Internet Movie Firearms Database is the go-to source for identifying firearms in movies and other media, including anime. The Trigun page says that the pistol that Vash and Knives carries is


  a fictional double-action, full-sized revolver chambered for .45 Long Colt.


The name is AGL Arms Factory .45 Long Colt.