I'd say
voxelstein its cheap because its free, and I dont know anyone who knows what voxelstien is. I had to tell them what it is.
Its basically a 3d remake of wolfenstein but instead of pixels its
VOXELS. That means, Full destructable environment. I've waited years to be able to cut a hole in a wall with a knife then shoot an enemy through it. Jesus christ this game is awesome. Its made in the
Voxlap engine. And fairly easy to edit.
Keep in mind though, Its only in beta. One level.
Screens:





If you've ever played wolfenstein 3D, and know the cheat code... That cheat code works on this too :D