Now ubiquitous in science fiction, the idea of the space marine probably began its popularity after James Cameron's 1986 film Aliens, but was introduced much more recently, possibly as early as the 1930's.
The archetypical space marine always has an assault rifle, which has a very large clip to account for its ridiculous firing rate. This large gun is presumably used to shoot aliens, which are, of course, always hostile. Despite its incredible rate of ammo depletion, the marine's weapons are rarely very effective against anything other than small rodents and other space marines.
Space marines are also known for their colorful vocabulary, witty comments even in the heat of battle, and high-tech body armor. Selfless heroes, they always fight to the bitter end (or die trying to run away).
Space marines have been spotted in the following locations, among others:
- Alien and its various sequels
- Starship Troopers was originally a book by Robert Heinlein (written in 1959), and was later adapted to a movie in 1997. The book is a good early reference to the ideal space marine.
- Doom. While not the typical space marine, the character in Doom did fight off legions of aliens in a suit of armor.
- Warhammer 40K (and all its variations; please see accompanying node text)
Thanks to wharfinger and dido for contributions.