It's an unusual entry for an RPG, but my all time favorite RPG has no swords or spells at all -- only spaceships. Star Control 2 was an ingenious romp through space, collecting minerals and interacting with a rich universe full of aliens (some friendly, some not). Sadly, the sequel was a complete bastardization of the goodness of #2, and any further development on the line stopped with #3.

However, it's been ported, for free -- check http://sc2.sourceforge.net/downloads.html for a hit of space-faring RPG goodness.

You will rue the day you opposed me! Begin your rueing! I'll just... sit over here... and watch.