In Ragdoll Deathmatch (RDM), you control a ragdoll that you try to run into other ragdolls with. Hitting other ragdolls with your hands or feet will do damage. The last ragdoll standing (or floating) wins!
A small test demonstrating the movement of RDM. Note that it looks like it is derived from sandbox in the video, but it is actually derived from fretta (due to problems with Source Recorder. I'll have it fixed in the next video). Also, the mouse doesn't appear in this, but it is there. It just doesn't show because of the problem with Source Recorder.