Voxel means 3D pixel, so dont start calling 2D games like Terraria "Voxel" games.
This thread should be called "Geometry based game ideas" simply to allow both 2D and 3D ideas.
Anyway: I'm working on a 2D space game, where NPCs are softbodies and the player can build robots, wire them together and cause havok on nearby planets.
The player's ship is made of different blocks (Like pipes, thrusters, cables, iron, lights, weapons, switches, wirable blocks) constrained together.
I'm not sure if this game will ever see the sunlight, but if it does: I sure could do with some support, I might even go as far to say its going to be fun.