One of the most popular races in the table top game, Warhammer 40k. Space marines are basically super soldiers with power armor. The reason for their popularity is
1. Their tactics are fairly straight forward.
2. They are easy to paint.
3. Easy on the wallet since you don't need many of them to have an effective army.
4. They are hella tough.
Damn, he just raped my orc army with his space marines because my orcs have a fucking stupid 6+ save and are raped by bolters.