Shadowdancer said:Traveller T20 Handbook. There is so much usable stuff in there for non-Traveller games, esp. games involving space travel. But the design systems allow you to create technology items for any tech level. Star system design system allows you to create solar systems for any system. Ship design system allows you create star ships for any system. Trade system can be used to handle trading for any system.
Easily Transhuman Space [suplements] and Biotech.Jürgen Hubert said:Since many here seem to like GURPS, what are the GURPS 3e supplements that you have gotten the most value out of?

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.