Space / Medieval Engineers
Let me start off by saying Keen Software House has nailed what a voxel sandbox game should be these days with their two, similar in play but different in settings, sandbox building games. In both you play an engineer tasked with building spacecraft/space stations or castles/forts/towns and catapults respectively.
Both run on the same engine that allows structures to be destroyed progressivly so to speak. So fire a boulder at a castle wall and you will see the boulder break bits of the building off instead of the whole piece just falling to bits. Its a fun game where your imagination is really your only limit.
Check it out here: http://store.steampowered.com/app/333950/
Pixel Piracy is a side-scrolling 2d, real time strategy/sandbox/simulation game created by indie developer Vitali Kirpu and Alexander Poysky. You get to start off as a pirate captian and are able to recruit other pirates as well. The game allows you to build a ship block by block and sail it into sea where youll encounter other pirates and visit islands. But the game is not without a comedic taste. For example your pirates will over time litter the poop deck well….with poop. There is an actual skill you can teach your fellow pirates that allows them to keep the poop deck clean.
Find it here: http://store.steampowered.com/app/264140/
In Prison Architect, well the name says most of it. You get to build and manage your very own maximum security prison. Hire staff, stop prison riots, get grant money from the government for building an electric chair. It reminds me quite a bit of Theme Hospital, so if your into manageing and building things this one is for you.
Check it out here: http://store.steampowered.com/app/233450/
Surgeon Simulator 2013
Fair warning, Surgeon Simulator 2013 will not teach you how to be a surgeon, sorry Frank. Anyways, Surgeon Simulator 2013 allows you take the role of a surgeon but you get to control a hand that has the fingers mapped to different keys on your keyboard making it quite the challenge to pick up tools and items. You’ll perform a multitude of different surgery’s from a heart transplant, to brain surgery, to dissecting an alien.
Find it here: http://store.steampowered.com/app/233720/