Seeing that this is kind of a place where people play a science fiction space game a lot, I am rather surprised that no one here has mentioned a mod for Sins of a Solar Empire: Rebellion called Star Trek Armada 3.
I have been playing it for a couple months now, it is pretty fun, and surprisingly well made actually. So far they have 4 playable factions from Star Trek, the Federation who focus a lot on the economy, diplomacy, and relatively well rounded ships with some expensive research... the Klingons, who focus a lot on lots of faster ships with lots of weapons and a bit less survivability and they get some good mining bonuses... the Romulans, who can tech up very fast and cheaply, operate at superior levels of intel, and colonize quickly and bring ships in with long range weapons and lots of debuffing abilities... and the Borg, a very slow to get moving but ultimately supremely powerful faction which can outgun and outtank just about everything out there, you need to team up against them because one Borg cube is going to take out several dozen ships by itself without effort.
The mod pays a lot of attention to detail, they have removed most stock assets from Sins, adding their own UIs, voice acting, sound effects, icons, music, etc... the devs are already working on an expansion to the mod which will add the Dominion/Cardassian forces.
The mod has constantly been within the top 10 popularity on ModDB, it has been featured in PC Gamer, covered by Totalbiscuit, and well it is probably worth the attention. It is a ton of fun and just a real pleasure to play a functional and enjoyable Star Trek game where there have really been none in so long.
