biographical article needs additional citations for verification. Please help by adding reliable sources. Contentious material about living persons that is unsourced or poorly sourced must be removed immediately, especially if potentially libelous or harmful. (August 2010) Gary McCormack is a Scottish actor. He is best known for portraying "Larry" in Paul McGuigan's 1998 film The Acid House, written by Irvine Welsh. McCormack won a 1999 International Fantasy Film Award for Best Actor for his role. He is now working on his new film Valhallan shot in Glasgow. He also starred in River City as gangster, JP. He is a resident of Leith, Edinburgh..