Wild Bill Hancock, a sheriff, was killed during an illegal poker game, and the 'Ace of Spades' alludes to the poker hand he held when he was dead.
With this song, Motörhead ensured their place in music history, the song's profound significance and memorable title standing on their own. If you're a real metalhead, you probably have 'Ace of Spades' by Motörhead on your playlist.