A while ago, there was a server called EVO Hardkour Parkour. This server ran the Parkour gamemode, which was absolutely awesome. If you've heard of it, you can skip this little part here...
The parkour gamemode was commonly played on the map "bigcity". Pretty much, the main focus of the game was that you ran up to a wall and pressed keys, and you would go up the wall. For example, if a wall was on your right, you ran up to it, jumped, and then held 'w' and 'd' and spammed 'a', and you would fly right up it.
There were many neat features the server had. Mainly, there were 'teams', which were just mini-games that you would join and gain different objectives/load-outs. For example, there was the weaponless "Hunted" mini-game, where one person was it, and everyone else on the mini-game would have to chase and tag the Hunted. Once the Hunted was tagged, he died, and the tagger became the new Hunted. Another mini-game was "CTF", which is pretty self-explanatory, except in this, you had guns. Of course, if you didn't feel like doing games, you could be a "Freerunner" and just practice flying around. Each of these gamemodes gave the player a colored trail, such as orange for the hunted and blue for the hunters, white and black for CTF, and red for DM.
Something neat this server had was an in-game dj. This dj would have music submitted on the forums by members, and you would buy song-plays with points (I'll get to that) to let you add a song to the 'To Play' list. I believe this was called "Wolf DJ".
I mentioned points just a second ago. Every 10 minutes, you got 20 points on the server. You could also get points by doing mini-games, such as capping the flag or tagging the Hunted. These points were used to buy song-plays, hats (melon, bucket, skull, etc.), and player trails for Freerunner (I could see us using rank-specific trails, such as VIP's and Admins getting VIP and Admin trails, respectively. Also, if we really want to go this far, I can see the points as being something potentially purchasable on the website.
If this ends up actually going forth, which I really hope it does, the dude programming the game may contact me for more exact details on how the server can be reborn (I can't program worth squat; if I could, I would have done this). I think it would be a very popular server, seeing as how a lot of the Gmod community knows about parkour, but hasn't been able to find a server lately. It would be awesome (though ambitious) to see this actually happen! :)
--EDIT--
I have found a brand new parkour server. It's pretty different, but neat, but different. I still think it would be neat to have our own...