Planetside 2.
If you're in to FPS's and have a decent rig (or a moderately decent rig, I'd recommend a 5770 or higher with a quad core at the minimum, I barely get by) this game is amazing. And it's free. The catch is that new players are really heavily gimped (weakened) by their inability to have good weapons and armor and upgrades. If you want to have a better chance and not be killed all the time, you have to come off of some cash. It's actually pretty tempting especially for people like me who don't want to spend too much time earning points to upgrade (you earn points for all your kills, or repairs, or healing that you do, which can be spent, like money, to upgrade your character).
This past weekend they were doing a "double XP" thing where you got twice as many points for whatever you did that earns points. So I played it. A lot. Generally you join a squad if you want to understand what's happening and have a better chance of surviving. This game is not a "go it alone" game! (Except if you play as an infiltrator, but you will die, a lot. And that can be really demoralizing.)
I'll give you two play experiences that I had. One time I was with a squad and we'd taken over the "Crown" a place on one of the continents (I should say, this game takes place over a few thousand square miles of seamlessly integrated landscape!). I forgot the name of the continent so I'll leave that there. Anyway, the Crown is normally held by Terran because we have a quick route to get there and pull a surprise attack (and it's through mountains so ambushes are quite uncommon). One of the squad leaders decided we should just leave Crown and take over Vanu space to the west. Every single person, over 200+ left. We marched west as the rest of the game space wondered what the heck we were doing. We dominated the entire space because all the units were concentrated at Crown and they wanted to take Crown and get XP for doing so. Every single scuffle we destroyed, hundreds of units, like an RTS, but with actual people. Nothing could get in our way. Of course, the further you are from your territory the harder it is to hold on to it (you have to take over bases, which can be convoluted with the more intensely guarded basis, such as first destroying generators, etc). So our resources slowly dwindled. We'd almost made it entirely into Vanu's territory, cutting them off entirely, when our forces became so small as to be unsupportable (and others left the grouping to go earn XP at other skirmishes after they got bored with it). But the experience was monumental. I kept spamming the chat feed "This is epic!" as others cheered and agreed and said they never saw anything like that or were part of anything like that before. It was really a grand old time.
The other, less interesting or exciting play experience I had was as an infiltrator. Infiltrators can go almost completely invisible for a short period of time. If you weren't focused on the player when they went invisible, you won't be able to track them. There is a very faint transparency there, so it's possible to see them when they move, but only if you have spotted them initially. It's impossible for the eye to make out the movement if you're not following it. Anyway, infiltrators jobs tend to be to get into the larger bases and overdrive the generators so they explode and the shields go down so you can then have your forces engage (all the big bases have these force fields that only infiltrators can get through). So here I am, wanting to get to this base, and there's this massive battle going on with over 200+ players. Missiles, tanks, ships, whole nine yards, stuff exploding everywhere around me. I notice that there are a lot of bushes, and they appear to be incidentally placed just far enough that I can get to each one while staying invisible (unfortunately you cannot shoot while invisible, I should say). So I went invisible, bee-lined for a bush, and just as I got to it my cloak went down! Yes! They designed it this way! For this purpose! I kept on toward the base, squatting in a bush here or there when my cloak was nearly depleted or just depleting, sniping the occasional foot soldier. My heart was racing because as I got closer there were more and more opportunities to be spotted. A stream of hundreds of soldiers, either those respawning from dying, or others from elsewhere in Planetside kept spewing from the base. I couldn't infiltrate for anything! But I did. I did it in the most awesome way imaginable. A tank was returning to the base to get an engineer to heal it or maybe the driver wanted to become an engineer themselves to heal it (you have to go to these armories to change your abilities; though there are portable ones, this may have been unviable). So I get behind the tank, my cloak starts to dwindle a lot, it's in the red, and I see troops in front. I move to the left side of the tank, my cloak goes down, and I keep running, right behind the tank. They don't see me! My cloak recharges enough so that I can turn it on and just as the guy jumps out of the tank I am invisible! Pow, head shot! I die shortly after, the excitement of having someone in front of me without them knowing overrode my original intent to get inside the base and override the generators, playing the fun game of running back and forth, overriding them, someone comes and repairs it, run off, override another, like a big boy game of cat and mouse.
Fun times.
Try it out, it's free. And the urge to buy upgrades isn't that bad, if you're willing to just keep playing. You do have to put a lot of hours in if you aren't getting XP bonuses though.
http://www.planetside2.com/
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But I wouldn't give people the impression that you have to dedicate serious hours to get anywhere. I suggest to anyone starting out to just pick one class and one vehicle to specialize in. I also suggest spending $10 to get some station cash to buy weapons. Save all the certs for upgrades.
I just don't have enough time to get serious about this game but it is fun for a random pick-up game. Spawn in the warpgate, hit insert twice, and voila.. you're in a squad and in the action. Brilliant.
And if you're lucky, you get hooked up with a big outfit with multiple platoons. The 300-400+ person battles are breathtaking. Especially at night. Bio-dome battles at night are my fav.
Long live the NC. 
I just have bad luck that way. 
Craziest one I've seen so far was an air squad of eight or nine fighters and a few gunships who were obviously all mic'd in to one another and acting with downright eerie coordination. I was on the receiving end of that, which would normally suck to the point of being frustrating, but it was really amazing to see them in action.