http://www.spiralknights.com/ is a new free-to-play MMO that was just launched today, April 4th.
The game's a dungeon crawler set on an alien world. You play as a member of the spiral knights, some sort of space chivalric order that has crash landed on this bizarre place. Their ultimate goal now is to leave, and they intend to do so by stealing the planet's core to power their ship.
The game plays like a mix of Phantasy Star Online (Episodes 1 and 2) and Zelda - Four Swords, both for the gamecube - with controls reminiscent of Magicka. As mentioned it's a dungeon crawler - you join with up to three buddies and crawl through dungeons looking for items, cash, crystals - items used to power the dungeon elevators. The game itself has no stats, instead each item you have equipped can gain levels, although not necessarily 'grow' - they gain stats but not new abilities, at least as far as I can tell (kind of like 'grind'ing weapons in PSO - and no, it does not mean killing a bunch of dudes for one). Instead there's an alchemy system of sorts to craft rare items with special effects, and you can buy a bunch of lower-level ones with statuses too. For example I have a pistol that, when charged, stuns enemies. However to perform alchemy you need to acquire recipes.
Like PSO there are normal and 'heavy' attacks that require charging time. The heavy attacks seem to do more damage and inflict status effects very frequently. There are three weapon types and no classes - you can switch between weapons on the fly by tapping space. There are melee weapons (powerful, but you need to get up close and personal), guns (not as strong, and you move slower when reloading - you can fire a limited amount of times in rapid succession), and bombs (you charge them up and toss them).
Like Zelda - Four Swords, there are somewhat convoluted puzzles (at least for an MMO) - you can hit switches with your weapon or with thrown pots and statues to activate doors, locate keys, and that manner of thing. I spent a long time trying to hit a switch from offscreen before realizing that you could throw pots over ledges, for example. The combat is also much quicker and there is no lock on like in PSO - so you'd better be aiming that gun appropriately! And you can manually block if necessary.
As I mentioned before, there are crystals. The levels that are accessible at any given time are determined by the crystals people have 'fed' the elevators and I believe they reset every 24 hours. You have an unlimited inventory space, but you can only carry one crystal at a time.
When dungeon delving you can go it alone, only allow friends, or let the game 'matchmake' you with another party. For example my first dungeon run I ended up being party leader with 3 other people. Party management is fairly easy and allowed me to weed out a deadbeat quickly, once I realized I was the party leader.
The game is free-to-play, as mentioned, but the game attempts to make money through microtransactions, but thankfully it's not too game unbalancing (well, as far as I've noticed yet). To activate elevators you need to give them some 'power'. The dungeon I just ran solo required 10 power to descend each floor, for example. You have 100 power on you, it replenishes slowly over time and I believe whenever you log out and back in. However you can purchase power using in game cash or out of game cash. Power can be converted back to in-game cash if required. You can also purchase 'perks' like additional hot-swappable weapon slots and 'trinket' slots, but you can, again, purchase them with in-game cash.
I know at least one other person from B12 is playing this game right now - anyone else?