I recently came across this multiplayer deathmatch mod, which...
"...takes place inside of the same cube that was seen in the moive "Cube 2: Hyperucbe". It has traps from all three cube movies, and has been designed to simulate infinite cubes in a finite number of cubes. The object of the game is to simply, get out of the cube alive, and once your out, the game is stll not over!"
This is an exact quote, they mispelled "moive", not me.
I am downloading this now to see what it's like, and I encourage other HL2 owners to do the same. Screenshots will follow

Edit: forgot the URLs:
To download:
FilePlanet
For info:
Moddb