Warhammer 40,000, Copyright Games Workshop (r). Originally a tabletop game, it has expanded it's reach into the computer game industry (Space Hulk, Dawn of War 1 & 2) and console game industry (Squad Command, Space Hulk 2, Fire Warrior, Space Marine).
It consists of many races and even more factions. Though the tabletop game is highly expensive, complicated, and time consuming, the videogames are persistently more action/tactically oriented. All video games in the Warhammer 40,000 series (or simply WH40K) have been either real-time or turn-based strategy games, with the exceptions of Space Hulk 2 for the 3DO, Fire Warrior for the original Playstation, and the upcoming multi-platform Space Marine, all of which are first-person shooters.
You should really read into this stuff
A Space Marine, on that note, is a Psycho-genetically enhanced super-soldier with an age range of a few decades up to a few thousand years. They are power-armoured superknights who serve an immortal human being known simply as "The Emperor of Mankind". They wear thick carapace (full body) motorized armor (which can weigh anywhere from 50 to 10,000 pounds depending on type) and have a policy of killing everything that moves and is not human. They carry large guns called "Bolters" which fires self-accelerating rounds that explode inside the target. Though these are the Space Marines default weapons, more devastating weapons are available in their arsenal, and frequently Marines train to use these instead.
Needless to say, they are very hard to kill.
Some Space Marines:
A sweet Space Marine redesign by Prom:
