If you're like me, you probably bought a DSi at launch. If you're also like me, you probably thought DSiware was gonna be big. Now that the 3DS can pretty much buy and run any DSiware game, some of the lesser-known titles that were launched on the service should get some recognition.
Escapee Go! - 200 points
Escapee Go! plays sort of like Pac-Man. Only you're psychic. And the game has a plot. Features multiplayer, but no download play option as far as I know. It's a good game with a nice, pixelated art style. Give it a try.
Pop Island and Pop Island: Paperfield - 500 and 200 points respectively
Pop Island is pretty much the best, cheapest multiplayer experience you're going to get from DSiware. It's essentially Capture the Flag with cute animals and vehicles. The main draw to these games is that they have DS download play with up to seven other people. Get some friends together and it becomes insanely fun!
Spotto! - 200 points
This is a small game from Intelligent Systems. It's also adorable as hell. You play as Spotto, tossing bombs into the mouths of ghosts to save the daughter of the President, Chickie Wowwow. It's better than it sounds, trust me.
BlayzBloo Super Melee Brawlers Battle Royale - 500 points
Blayzbloo got a bit of flak when it was released, since it wasn't exactly very deep. It's still a very nice Powerstone-lite, especially if you can convince your friends to get it as well. The worst thing about this game is no DS Download Play, so everyone's going to have to pony up five bucks if they want multiplayer battles. Still highly recommended if you have friends who want to get it or are a Powerstone/Blazblue fan.
Go Series: PicDun - 500 points
PicDun, standing for Picture Dungeon, is seriously unique. You have the old-school dungeon crawler game with a little twist of Picross added to it. As you explore the dungeons, you solve puzzles and complete the map of each floor. Battles are a simple affair, either slashing or thrusting your sword at opponents as you block their attacks with your shield. Highly recommend it!
Dark Void Zero - 500 points
Better than the actual Dark Void game. It's a retraux side-scroller that's sorta reminiscent of Metroid and Blaster Master. Bosses are pretty cool, but the game is tough.
Dragon Quest Wars - 500 points
Intelligent Systems. They made Advance Wars and Fire Emblem. They also made this. No DS download play option, but online multiplayer makes up for it. Plus, it's a turn-based strategy game, so there's really no point in Download Play if you can just pass the system around.
There might have been some other games I missed, but these are some of the most entertaining that I have played. I know I didn't include any WayForward games like Shantae or Cave Story, but this is a list about lesser-known games. I think.