I refer you to the following threads:
Like I said in the other thread Aaron quoted, I tend to prefer skill-based systems over level-based systems for scifi and modern-day games.
My first choice would be GURPS. I've played in three or four sci-fi games using GURPS over the years, and the sytem really works well for the flavor.
Savage Worlds is another good choice. I've only played it a couple of times, but it also does a good job. It's a lot less crunchy than GURPS, letting you get into the action quicker.
If you'd rather go in the other direction with regard to crunchiness, there's HERO System.
I last played Traveller in the early 1990s, and had some major issues with the character generation system. If I recall correctly, it was a lot of rolling on numerous tables that let you pick from limited options. You couldn't go into character generation with an idea in mind: you had to retrofit the character's background and personality after the fact based on the disparate skills you picked up in your "training" (i.e. character generation). And you could actually die during character gen! I ended up with a character very different from the one I'd wanted to play, and my interest in the game suffered because of it. (On the plus side, I understand that they have greatly improved that aspect of the game over the last 20 years, but my early experience has quashed my interest in the system.)
Fate/Fate Accelerated Edition: If you want to focus more on story and less on crunchy mechanics. Character creation is wide open.
G.U.R.P.S.: If you want some serious Simulationist fun. Plenty of supplements for Science Fiction settings.
Hero: Crunchy system that allows for just about anything. Some support of Science Fiction settings.
None of these systems come with a pre-fabricated setting. All three can handle Psionics without collapsing into a heap of unfun.
I would not recommend G.U.R.P.S. or Hero for a one off campaign. There is a high learning curve that is a hard sell for a one time thing. Both systems are better tailored to being consistent playing platforms across multiple genres. If you are going to learn them, you might as well use them again and again.
Stars Without Number. It's easy to learn, it's free, and it's well-written.
@Golem101
There is a FATE Core conversion of Eclipse Phase coming.
Really? FATE is awesome. I cannot sing its praises highly enough(literally everything I want out of an RPG, to the point where anything other than Mythos horror, I'll probably be turning to fate to run). Well, in that case I'd try to see passed what ever it is you don't like about the eclipse phases system, because it is an awesome setting.
Also, if you haven't listened to the RPPR AP "Know Evil", you should definitely check it out HERE.
I really enjoyed Parsec.
Everything I mentioned in previous threads, plus Mini Six(distilled D6 system) if you want a quick lite game.
I have yet to run anything with it .
Also, if you haven't listened to the RPPR AP "Know Evil", you should definitely check it out HERE.
I was going to say that.
I really enjoyed Parsec.
Could you tell us more about it?
I saw the kickstarter (almost two years ago now?) but I haven't seen a single review since then