When visiting the gun range, Shawn introduces Gus as Gern Blanston. This is the same name that comedian Steve Martin "revealed" to be his real name to his audience on the comedy album "Comedy Is Not Pretty!"
At the gun range, there's a plaque on the wall indicating that Lassiter won 1st Place at the "Lucinda Barry Memorial Tournament". Lucinda Barry was Lassiter's partner in the pilot episode, portrayed by Anne Dudek. "Memorial" is likely an in-joke about the character being written off the show, as Barry tested poorly with audiences and was replaced in the second episode by Juliet O'Hara.