This entry to the list is a complete no-brainer, as anyone who has ever seen 1969's Butch Cassidy and the Sundance Kid knows how powerful the relationship is between the titular dynamic duo. The two men's endearing, consistent and occasionally hilarious closeness is apparent from the very beginning, established in Butch's interplay with Sundance directly before he has to defend his title as leader of the "Hole in the Wall Gang." From that point the connection between the two wily outlaws only becomes more absorbing. The audience spends basically the entire movie with the men, following them as they desperately attempt to elude relentless lawman Joe Lefors, or when they have a brief reprieve with Sundance's lover Etta Place, who is played here by the luminous Katherine Ross. Nearly every scene featuring the pair has a memorable quality to it, such as where Sundance finally bellows at Butch Cassidy that he can't swim right before they are set to leap off a cliff into a river. Of course, nothing is more emblematic of the two men or their friendship than the final scene, where they go down together, guns blazing.