I've been playing this nice indie game called La-Mulana. It's kind of like if the original metroid game was an Indiana Jones ripoff. It's extremely hard, with traps at every turn, many difficult puzzles and riddles, and some platforming that can be difficult at times. The game is very nonlinear, and there is pretty much no way to tell if you are going the right way, other than the steady progression of new items. To get a feel for the game, I suggest you watch a few of Deceased Crab's Let's Play videos, or, better yet, just download the game. It's free, so give it a shot.
If you have played and enjoyed games like Metroid, Castlevania, and other extremely nonlinear games, then you have to try this game. I've been plugging away at the game for over fifteen hours, and I don't think I will be done anytime soon.
Also, there is a Wiiware remake in the works. The release in Japan is on July 21. The US and EU releases are not yet scheduled, but the game will be released ouside of Japan. I wouldn't wait for the Wii version. They are making it easier, which I believe would kill the experience for first time players.
The game and an english patch can be found here.
The game is well translated. No engrish to worry about.
EDIT: Fixed release date. Thank you Stuff.