Burton "Gus" Guster is a fictional character on the USA Network television comedy Psych played by American actor Dulé Hill. He functions as the straight man for Shawn Spencer's antics, and provides sobering advice, steady support, and friendship. Over the course of the show, Gus evolves from nothing more than a conventional, uptight pharmaceutical representative to a strong support system through all Shawn Spencer's crazy antics. [from wikipedia]
A running gag on the show involves Shawn introducing Gus to suspects. Each episode brings at least one new made-up name for Gus. Sometimes funny, sometimes clever, this gag is one of the things that makes this a good show. Don't belive me? Watch the show some time.
Either way, feel free to check out some of the nom de Shawns we've seen so far: