Recently I have been playing a halflife 1 mod called Natural Selection (NS).
NS is basically a cross between Starcraft and AVP/AVP2 (Without the preds) in as much as there is both First Person AND Real Time Strategy play.
There are two teams, Marines and Aliens
Marines are like your standard 'Aliens' Marines, machine guns and welders etc. One marine can Command the rest of the team, the commander then plays the game from a top down RTS view, and builds structures, tells the marines where to go and organises the assault (or defense in a lot of cases) on the Aliens
The aliens are similar to the Aliens from the films, but also have interesting evolutionary differences.
Your standard alien can climb walls and ceilings, leap at their pray and bite heads off.
But they can also evolve into other forms, a builder/medic who creates structures for more resources, bases (hives) and upgrades like cloaking or regeneration for the team.
Theres some other alien types to evolve into, the most fun is the big fuck off elephant who digests the marines for health and only gets tickled by light machine gun fire.
You can view more info about the mod here - http://www.unknownworlds.com/ns/
Hopefully ive intrigued some of you enough to give it a go, the online community is still quite large with enough activity (50 times more than DX at the moment ¬_¬)
I usually play on the Marine Trainer servers, as they are basically human marines versus alien bots, the bots are good, but not as deadly or tactical as human played aliens
My alias is "MrBlack"
You may also find me on my own server which i host just so a couple of friends can get to know the game without the pressure of the NS pro's who may or may not give them "noob" shit
The server name is MrBlack's server, and the password is "yob"
You will need Steam and a VALID key of Halflife 1 to play this
If you have played Sven Coop then you should have the requirements to play this
Give me a shout on here or msn or wherever if you want a game!