Halocraft takes the multiplayer deathmatch mode from Halo and makes it all blocky.
A group of creators have followed up on Minecraft's PvP implementation by modding a Halo deathmatch mode into the title. Dubbed Halocraft, the mod features an actual Halo level, and actual Spartans running around shooting each other.
YouTube's SidolaTehNerd uploaded a video of the mod that shows him engaged in a deathmatch with another Minecraft player. They're running around a classic recreation of Halo 2's Lockout map. Sidola added in textures and sounds to give it the proper feel.
Sidola says the mod is run on a "simple hMod server." It gives players a gun when they spawn and uses kits for an allotment of ammunition. To handle death, the server links multiple teleport locations to one point so it can randomly generate a spawn location.
It's examples like this that show exactly why Minecraft is so popular. Marcus "Notch" Persson and Mojang Specifications haven't finished the game yet, but its structure allows players to create just about anything they want to keep themselves entertained in the meantime. Halo multiplayer on the Xbox 360 might look better, but there's an appeal to the simpler Minecraft version too.