One of the most recent additions is the WAR! update, which comprised of new unlocks for both the soldier and demoman. The latter class I barely ever play as because of my complete inability to face off against anyone coming directly after me. I've mostly taken to wearing a top hat and running around with a sword (which I got as a random drop). The soldier, however, is a bit more my speed. It's the most 'classic' of all the classes, as you get a shotgun and rocket launcher (and a nearly useless melee weapon). My main gripe with the soldier was always the speed of the rockets.
As a way of perhaps trying to keep them from being overpowered, soldiers can only chamber four rockets at a time and they are rather slow and the reload animation is fairly lengthy. My main issue was the rocket speed, as it forced most soldiers into a mid-to-short range game of shooting people in the feet. But no more! The new weapon, dubbed The Direct Hit, rewards people who hit guys directly. The damage is 25% higher and the speed is 80% greater, making them pretty fast. The downside is that there's almost no splash damage, so if you miss even by a little it's mostly wasted. I was never amazing at Quake 3, but I always enjoyed the hell out of it, with the rocket launcher being a primary reason.
None of the unlockable weapons are a huge improvement over what they replace. The scout's melee replacement, the Sandman, is a bat that's identical to the default one, except that you can also hit a baseball that stuns any enemies it hits from within a certain distance. The downside is that you have 30 hit points fewer, but with a scout that doesn't necessarily matter.
Some unlockables are just plain fun. The sniper can use a bow and arrow called the Huntsman. It's inferior to the sniper rifle in every way possible, except that you can shoot arrows which can pin bodies to the wall or stick out of them if you connect but fail to make a kill.
Valve deserves a lot of credit for breathing new life into this game on a pretty constant basis. It's not something many game companies could ever afford to do, which is why the situation is so unique. Since TF2's initial release I've dropped it and come back a number of times (probably four or five), when generally with online multiplayer games the first time I drop it ends up being the only time.
It's not a game that was released in 2009, but it's certainly one that I enjoyed a lot in 2009, and that's pretty cool.