If you have had enuff of doing the same old thing on HL2, CSS etc, check out the Empires mod (http://www.empiresmod.com/)

This attempt at combining a FPS with a RTS can offer some fantastic team-based action.  Of course, when the team fails to coordinate it can also suck, but you are all familiar with that scenario, I'm sure.  Many maps/missions are about building up the teams resources so you can be the first to build the biggest nastiest tanks, then stomp all over the opponents.  Other maps are based on a variety of territory-grab and defense missions.  If you enjoy building sentry guns in TF2, you may find this more fun, with both anti-personel and anti-vehicle turrets.

Vaguely reminiscent of Tribes with the open landscapes, but with tanks and no flying craft (yet) but sadly it is currently lacking an active following in the NZ/Aus region, so I have to play on some distant and laggy servers.  Would love to see some local servers start to fill up.  Give it a try, go on, you know you want to.