The Mass Effect series gives you a pretty flabbergasting number of worlds to explore, but what's a sci-fi epic without an ice world? Noveria is a tiny, frozen world that's barely habitated - but its few residents are an interesting lot.
Fully owned by the Noveria Development Company, the world is used for performing scientific research that would be considered quasi-legal in Colonial space. You're dispatched there to investigate reports of geth activity, but you'll find a lot of challenge there.
The first PC release of the game had a ton of bugs in this area, but they have thankfully been mostly patched out. It's a pretty cool world.
