In Indiana Jones and the Kingdom of the Crystal Skull, O'Neill was one of the stunt doubles for Shia LaBeouf who portrayed Mutt Williams. O'Neill also doubled LaBeouf in the 2008 motion picture Eagle Eye (2008). Among the other actors he also doubled are Antonio Banderas, Tom Cruise and Colin Farrell. He was responsible for supervising the horse stunt riding sequences in the Lord of the Rings trilogy for filmmaker Peter Jackson.