Being There (1979)

Peter Sellers plays Chance, a gardener whose knowledge of the world comes entirely from television, and he plays him with total, unblinking sincerity. Washington's powerful mistake his remarks about the garden for deep wisdom, and the film never nudges you to laugh: it lets each misunderstanding sit until it turns absurd. Sellers was nominated for Best Actor, and Melvyn Douglas won Best Supporting Actor as the wealthy man who takes Chance into his confidence. Pick this if you like satire that keeps a perfectly straight face from first scene to last.