Butch Cassidy to Thelma & Louise to Sideways. The films built around the central friendship rather than around the central romance.
The buddy film is the genre whose central dramatic relationship is non-romantic friendship between two leads. The form is older than cinema (the buddy pairing exists in literature and theatre going back to antiquity) but is one of mainstream cinema's most-reliable categories. The films on this list are the ones that earned their pairings rather than treating the buddy structure as commercial template.
Our picks.
Buddy films succeed when the central friendship is dramatically substantial rather than logistically convenient. The pair's specific differences should produce the film's central tension; the pair's specific similarities should produce the film's emotional substance. Butch and Sundance work because their temperaments differ in specific ways that the film's plot dramatises. Thelma and Louise work because the journey progressively reveals their different orientations to the patriarchal world they are escaping. The Dude and Walter work because their separate relationships to American masculinity produce the film's specific comic register.
The films that fail at the form treat the buddy structure as scaffolding for unrelated material. The pair is reduced to two-cop-archetype convention; the differences are surface; the friendship is asserted rather than dramatised. The films on this list mostly avoid this trap.