The Walls is modification for Minecraft that adds a PvP survival mode. Word is: "The map is separated by giant sand walls, players start each on their own platforms and when the timer reach 00:00, the walls falls and the player can kill each others. The last man standing wins the game." This trailer offers a look at the mod in action. Thanks Ant via Reddit.
Seems the site is down. By the way where does one go to get Minecraft downloads that don't require the installation of some bloatware downloader and/or spyware? Seems the several sites I tried where full of the shit and won't allow you to just download the mods.