Get the Rival-Species v1.0 Mod Off Worthplaying (37mb)
For those of you who don't know, Rival-Species is based around the popular Warhammer 40K universe, and pits you against three possible races, the righteous fury of Imperial Space Marines, the unquestionable evil of their Chaos Marine counterparts, and the technological superiority of the alien Eldar.
Rival-Species allows you to take part as one of a veritable plethora of warriors for these races, with all the wargear associated with them. One of the most important aspects of gameplay is the "command" feature, where the leader of the team will select the forces he wishes to fight for the battle, thus adjusting your choice of class, don't worry though, they're all perfectly deadly!
Two little bits of advice; if you wish to see RS in all it's glory, you should customise the particle detail settings before playing, and don't forget to read the manual, there is a lot of important detail within.