I keep coming back to this wonderful puzzle game, and it does not disappoint.

User Rating: 9.5 | Rittai Picross DS
Who would have thought that manipulating a bunch of cubes could be so fun? I bought this game when it first came out in Japan in March 2009, and had I not lost it last autumn I would still be playing it. Needless to say I will be buying the US release.
The game begins out with a very helpful tutorial, showing you the ropes and giving tips on how to efficiently solve the puzzles. It might take a bit of time to wrap your mind around the play mechanics, but trust me when I say it is worth every second. Essentially your task is to chisel away at pixel-like cubes of a cuboid in order to reveal the figure inside, much like sculpting.
The different sorts of challenges (e.g., time trials or giant puzzles) applied to the huge number of puzzles are sure to keep you playing for some time. The Wi-Fi connectivity allows you to download hundreds of additional puzzles at any tim, ensuring that you will keep coming back to this fantastic game.
If I had to raise a complaint, I'd say that the solutions are often too blocky-looking and abstract for my liking. However with the limited size of the puzzles (maximum 10x10 cubes) that is surely unavoidable and is only an aesthetic quibble.
I highly recommend this game to anyone who would like to get some serious use out of his or her DS.