I know the "preferred" rules sets for MP tend to be either MP itself or one of it's close rules analogs (Twilight 2000, etc), but what other rules have people been using?
I put together a game based around the old Star Frontiers rules. I wanted a faster paced, "details light" game that didn't spend so much time on micro-computing damage by round type, gun type, etc. More of a focus on role-playing and less "accounting".
You can find a fan-pro revision of the classic rules here:
http://www.starfrontiersman.com/downloads/remastered
on one of the other pages on the site are fan-pro e-zines with a lot more weapons, gear, race/species, etc.