Ever since I started programming, I have always wanted to make a Capture The Flag version of ZDoom. Recently, I've been digging through my hard drive and found an old copy of a CTF version of ZDoom I made. Of course, with little programming experience back then, I was stuck on a few small things, but since I gained experience, I finished it off.
ZDoomCTF is ZDoom with a powerful Capture The Flag system, in which you can create custom teams, custom flags and have all the normal ZDoom features too. You can choose two team CTF, three team, four team, as many as you like!
You may be wondering if it is really worth going to all the trouble of making a CTF port with the current state of the net code. Well absolutely! If you watch the demo included, you can see a two team, four player CTF game in action. We all did have quite a bit of fun there. (Although I still can't believe that my team lost.

At the moment, ZDoomCTF is based of ZDoom revision 893 but I will be upgrading in future releases.
To run online here's what I suggest:
1. Set your teams up in advance.
2. Add '-ctf' to the command line.
3. Add '-file zdoom-ctf.wad' to the command line.
4. Add '+map D2CTF1' to the command line.
The 'zdoom-ctf.wad' is deliberately not automatically loaded as it serves as an example WAD for people creating their own Capture The Flag maps.
Bugs and possible features:
No bugs are known as of yet, but if anyone finds any then please either PM me or post in this thread. Thanks!
In the future, I may consider adding support for One Flag CTF, in which you take a white flag and bring it to an opponents base. Don't expect this anytime soon though.
Download:
ZDoomCTF Version 0.1 - 1.57MB
ZDoomCTF Version 0.1 Source Code - I'll get round to uploading this when my connection doesn't keep cutting out.