Pulp Fiction (1994)
One of the most important and influential movies of the 1990s, of course, with Willis in a role that lets him put all his talents on display at once. As a boxer named Butch who's supposed to throw a fight but ends up winning it instead, Willis is tough but tender, powerful yet vulnerable. Quentin Tarantino is in love with words and Willis is an excellent fit for his peculiar brand of verbosity; he's also very much up for the, um, many freaky and physical demands of appearing in a Tarantino film.
In picture: Bruce Willis with co-star John Travolta.