|'Crystal Castles' for Unreal One, 'Crystal Chaos' for UT2k4.
This total conversion mod is based on an old 80's Atari game, where your main goal is to snatch gems and crystals. It is amazing what you can do with the Unreal engine, and I have participated in the creation of this fun to play mod.
For the UT2k4 development, our team even participated in the Make Something Unreal Contest - we didn't get into the finals nor did we win anything, but we got an honorary mention once, which is more than a lot of other mods received.
This mod has its own page for both the Unreal One and UT2k4 version, so please go ahead to it (you will have to pick between Unreal/UT2k4).