Murder Miners just released to Xbox Live Indie Games. It'll cost 240 Microsoft points ($3). The game is a voxel-based first-person shooter with fully destructible/constructable environments, up to 20 players online, deathmatch, zombie survival & map creation mode. Infection, CTF, Juggernaut, Oddball modes coming later.
http://youtu.be/XR0S26CdLpQ
Screenshots