The Public Enemy is a 1931 pre-code gangster movie directed by William Wellman and starring James Cagney, Jean Harlow, Edward Woods, Joan Blondell. It is exactly what you might expect, but you already knew that by the cast list. This is one of those "best" films you see in lists.
It's listed in the book 1,001 Movies You Must See Before You Die. FilmSite calls it "one of the earliest and best of the gangster films from Warner Bros. in the thirties." Rotten Tomatoes has a critics score of 100%.