This is one of my favourite MP mods EVER. And before starting, I'm aware of Q3 Jailbreak, but after playing the UT versions, it feels... empty. Moreover, the UT versions have more "personallity".
It's a team-based, round-based gametype. Each team has an own base, with a release switch inside of it, and a jail, located either inside of the own base, on the enemy base, or in the middle area.
The players must frag their enemies in order to send them to the jail. Players can escape the jail by way of a teammate using the release switch in order to open the doors/bar/whatever.
Once all the players of a team are jailed, the opposing team scores a point, the jailed team members are executed (there are plenty of ways such as fire, poison, throwing them into void/lava or slime pits, crushing them with walls or spikes, etc), and a new round starts. The game ends either by reaching the capturelimit or having the highest amount of points after reaching the timelimit.
The UT/UT200X/UT3 versions of the mod added more features such as jail cameras (for jailed players to watch selected areas) llama hunt (for players who try to cheat by disconnecting themselves or those who shot just released enemy players) and the radar.
Needed entities... obviously trigger_release, func_button_release, trigger_execute, func_door_execute.
Here's a video:
http://www.youtube.com/watch?v=NUAbTSKtuAkSo, what do you think? And what more would you add to it?