5. Christopher Walken in 'Pulp Fiction' (1994)
In Pulp Fiction, Captain Koons (Christopher Walken) regales young Butch with a tale involving a gold watch that he smuggled in his rectum for two years. Without a doubt, it's one of the most cringe-inducing and unforgettable cameos ever. For another example of a Walken appearance guaranteed to make you squirm, see his scene opposite Dennis Hopper in True Romance.