I've run Star Trek in many different game systems over the years... FASA, HERO, Traveller (in a HOST of editions and revisions), Prime Directive, BRP, and some d20. My point being that (as has been implied), the system you use to play *your* Star Trek game needs to serve how you want your game to feel. One of the things I love about using the Star Trek Universe is how adaptable and versatile it can be towards different stories and styles of play. The source material is so ingrained into our Pop Culture that as a GM, you can take some explanatory shortcuts and fill in your players with a lot of background in only a few short statements. (If you're running a Star Trek game, there is little need to explain what Ferengi are, or who Q is). This quality allows me to be truly creative in adapting different systems to my player's gaming style. If the players are a detail-oriented bunch who enjoys defined rules for all situations, use a crunchy rules-system like HERO or GURPS or a d20 variant. If you have a gaming crew in love with narrative and loosey-goosey rules structure, use a Cypher System or FATE, or even Fudge or Dread. In so many ways it doesn't matter if my groups definition of Phasers set to Stun match your groups definition, so long as both our groups are having fun. Then we can all come back to Forums like these and tell our tales.