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 image is released on a CC-BY-ND 3.0 license
I don't know much about this ship, but it does look awesome. I assume the things up top are intended to be giant 2D turrets.
Cheers,
-Dirk