Kobold mines
Kobold Mines is a coffeebreak roguelike created by user:eyenot. It's also a three-day roguelike. It's written in C and originally uses curses, though there's a win32 version available as source or binary. Its creation was inspired by the August, 2008 2krl (2,048-byte roguelike) challenge on rgrd (rec.games.roguelike.development), but it became too large for that.
The player dives into the 16-floor mines in an attempt to collect cobalt. The main mechanism is the use of the miner's "hammer", which depletes the player's hammer store. The hammer can be used to break away a wall or destroy an enemy, though the number of other hammers lying around the floor of the mines is random so replenishment isn't always a given.
The two enemy types are kobolds ('k') and beholders ('B'). Both move around the floor trying to get closer to the player. Whereas kobolds have to occupy a space with the player to kill the player, beholders only need to have a clear line of sight to the player for a full turn to kill the player.
There's more to the game than is explained here or in the info text. The author is semi-actively developing the code and there may be a version '2' out in 2008.
The webpage is http://www.lunarsurf.com/~eyenot/kobmine.html
The software is completely free.