This is a World War II FPS, while it's an older game it's also a fun one.

You are either Axis or Allies competing against each other on various battlefield.  You have weapons of the period, and if there is a vehicle (trucks, tank, planes, or ships) you can drive, fly or sail it. 

We are currently running v1.61b, so you can find the updates links below, after you install the BF1942, download and install in order and you should be fine.

1.  BF1942 1.6.19 patch
2.  BF1942 1.6 to 1.62b patch

Note - A common issue we've run into with this game is having it crash while loading into multiplayer maps, make sure that you go in and save your video and sound settings.  While this doesn't work for every case on every map, it helps with the majority of the games and game mods.

Desert Combat is a modern take on on the Battlefield 1942 story line, with a marine vs insurgent type combat.  DC has the same kind of vehicle setup as BF, in the respects of being able to drive every vehicle you see, with new vehicle types (jets and tanks) as well as some all new types of vehicles (helicopters).

Once you have Battlefield 1942 installed and set up you can download and install below...

1.  Desert Combat 0.7
2.  Desert Combat Final

Note - A common issue we've run into with this game is having it crash while loading into multiplayer maps, make sure that you go in and save your video and sound settings.  While this doesn't work for every case on every map, it helps with the majority of the games and game mods.

Fortress Forever is a new spin on the old classic Quake: Team Fortress, it has all the regular classes (Spy, Sniper, Soldier, etc...). 

Play typically consists of capture the flag or push styles, with the maturer players getting dominated by the less mature (Dads getting slain by their children for example).

This game requires the source engine (Half-Life 2 or Counter-Strike: Source), but like Hidden: Source it's a mod that is external to Steam, but you should be able to find it for free here.

A modern day marine vs insurgent style mod to Half-Life 2 (requires CS:S or HL2:DM) that is freely available through the Steam Store.  With weapons that vary from sniper/marksman to grenade launcher/RPG's, as well as an assortment of machine guns in between, game play typically falls into a push style game (kind of like king of the hill) or a capture/defend different capture points of the map.  With use of iron sights and scopes, but no crosshairs, opinions of the game seem to fall into "I love this game" or "I'm going to burn down the developers homes"^*.

This one is another that may get some play, but it will have to depend on the general mood of the group.

^{* In part a total exaggeration}