Knox -
You might want to try out The World Ends With You. It's an action/RPG from the boys at Square Enix (the guys behind Final Fantasy).
There are tons of puzzle games out for the DS. Some of the more notable ones are Planet Puzzle League, Professor Layton and the Curious Village (very good), Picross DS (you can play something like this online on the PC for free, though I'm not sure where), and Puzzle Quest: Challenge of the Warlords. For the most part, the popular puzzle games on the DS are almost univerally good.
Ninja Gaiden: Dragon Sword is actually pretty fun, and it plays pretty well, too.
Other than these games, the only ones I own are New Super Mario Bros., Mario Kart DS, and Brain Age 2, all of which are pretty good.
I hope that helps a little.
Edit: Okay, I'm stupid. The Picross-type game you can play on the PC is called "Armor Picross 2." You can find it on Addicting Games, so you can try it out and see if it tickles your fancy.
-- Larry