Cardinal Quest 2 came out on iOS a few days ago, and I've been playing it pretty much nonstop since then. It's really well designed, not only the game itself (I never played the first one so I don't know what's different about it), but I've been pleasantly surprised on how well it works on a touch screen too (the one problem I've encountered is that sometimes when I try to tap an enemy next to me to attack them, I tap myself and skip a turn instead). I've played a couple of other roguelikes on my phone so far that haven't really clicked, but CQ2's controls work well, and the gameplay is fast-paced enough that it's easy to pick up and play "just one game."
I really like the fact that the classes play very differently. My favorite (that I've unlocked so far) is probably the thief. I like actually having to sneak around and stealth-kill monsters. The inventory and power systems are interesting too. Any character can use any item or spell, but you only have a certain amount of slots to store them in, and the spells recharge faster depending on your stats.
The game itself is free, but the classes and class upgrades are locked, but can be opened with "morale," that's gained from progressing in the game and completing achievements. Each class also has a unique way of gaining morale (thief gets it for stealth kills, wizard gets it for killing with spells, etc.). Of course, you can also pay money to get a large amount of morale at once. I'd be interested in seeing how that system works out profit-wise, because it's not very difficult to unlock things through playing, it just takes some time.
Unfortunately it looks like it's iOS only right now, but I think an Android port is coming. Has anyone else played it yet?