Dungeon crawlers and action RPGs have always been a favorite of mine, and Deadly Dungeon looks the part. The whole objective of the game is to find the portal to the next dungeon/level while killing a horde of monsters in each area of the dungeon.
It is free today in collaboration with the OpenFeint Free Game of the Day, and while it is a bit repetitive, for free you should definitely try it out. It does provide for a few hours of hack-n-slashing fun, and it also has OpenFeint achievements to unlock. Please note that Deadly Dungeon should be free for only a few more hours, so be sure to pick it up if you decide to.