I've been playing Battlefield Heroes a lot lately. It's completely free in a twisted EA kind of sense, but I think it's still worth a look into. Quick review of the pros & cons.
Pros:
- Very nice graphics, even if very similar to TF2. Runs nicely on little hardware.
- Good number of players allowed in servers.
- Easy controls, as with any FPS, simply point and click on people until they fall down.
- Simple, old fashioned fun.
- Fantastic music.
- Free...ish.
Cons:
- You cannot choose the servers you join, so you can end up in a very laggy server or with people way above your skill level.
- You can't change characters mid-game. This can end up with an entire team made up of Commandos (re: Spies with sniper rifles).
- I still can't work out how you win. Flags have multipliers underneath whilst there are points on either side that go up and down how they please.
- Weapon damage is sporadic. A sticky dynamite can take down a tank in 1-2 hits, but will only do a tiny amount of damage to infantry. Running people down will often just result in them flying with no damage taken. The pistol I have for my soldier has been known to take down snipers at great distances.
- You need to pay real money to buy points in order to buy the good weapons and clothes.
- Unless you pay real money, you never actual own anything. You rent it for a week or a month.
I'm sure EA will sort some of the issues out, but even so it's still fun. And free.