Here's a little interesting bit of obscure Valve knowledge; it seems that Valve wanted to release a port of THE famous Quake CTF mod; Threewave, to Deathmatch Classic at one point. It seems this port was released as a part of the infamous 2003 Valve leaks with the then full version of Counter-Strike: Condition Zero. It was lost in the commotion about the leaks until 8 years later, when SiPlus rediscovered it on a pirated Russian CD containing it with the leaked Condition Zero and a regular pirated HL1 copy.
It seems that this is completely legit; the “last modified” dates on the files were on 9/26/2003, which is exactly around the time the Valve leak happened. The artwork (well, the textures at least) looks exactly like the work you see in DMC, meaning it had to have come from Valve.
As for the actual content; the game seems to be in a heavily WIP state at the point it was leaked. All of the models for the runes and the Grappling Hook are ripped from the Quake 2 version of Threewave. The “original” models in the game consist of a reskinned TFC flag for...the flag and a blue or red Gman with their respective team's logo pasted onto his back. The maps go from perfectly retextured versions of existing Quake 1 CTF levels to basically raw ports of the original Quake versions with missing textures and broken spawn points. There's also a lot of neat-looking art for the new levels that've never been seen before, such as glass windows showing each team's logo, “techbase” textures that didn't appear anywhere else, a neat-looking skybox texture, and rock textures that look more like early versions of work you'd see in HL2 instead of the ones in HL1.
There really isn't much to say about the DMC Threewave port as a game, but it does show an part of Valve's game history they've never, ever told us about before; that they were planning on making a CTF mod for DMC. Interestingly enough, the original creator of Threewave works at Valve now. When contacted about this port, he said that there was never any plan to release Threewave to DMC. Makes you wonder if this was done behind his back as a side-project between a few guys.
You can download it at http://www.moddb.com/games/deathmatc.../threewave-ctf, but you need to own DMC and make sure you follow the instructions on the page if you want it to work.
Here's some screenshots :
(Nearly) Complete levels:
Really broken levels: