ScrumbleShip is the most accurate space combat simulation devised to date. Gather resources, construct a capital ship out of individual blocks, then pilot it with AI or human help against other players.
This game has extreme potential, and may be able to redefine the way we think about space games. It is also extremely mod-able, and easy to learn. Even with just the content already existing, trying to make a working ship is a lot of fun. The concept behind this game is essentially to cater to the wish of every space game player ever; give them the ability to make their own ships, stations, and more, then tie that into a large persistent universe. I can easily predict that if this game stays the course, it will become what us gamers have always wanted in our space sims.
Don't take my word for it, grab the demo or even the full game!