Toribash
Original Post
Starmade
It's Minecraft in space.
Wait no it's not, it just looks like that. A sandbox builder/shooter in space, fun game mechanics, the ability to build a huge fleet or maybe just a gigantic destroyer, space stations etc.
http://star-made.org/

Download this, it's free as it's alpha!
If you're already playing, post pics of your stuff so far!

(Someone with a good comp and net should make a server for us)
Try giving it 2056MB, and turning all settings down/off.
Worth a shot.

Also SP is laggier than MP (for me).