Goomba is a Gameboy emulator for the Gameboy Advance. Beyond the advantage of being able to store many games on one cart, Goomba also includes save states and customizable borders. At least, Kuwanger's fork does. Also available are many palettes, along with the ability to make your own. Read more about Goomba Paletted v2.37 (GB emu for GBA)
Shock Troopers Base Defense by Hokutoy is another game, based upon a "Tower Defense" concept. Defend your military bases and troops! A big amount of various enemies is guaranteed. Read more about Shock Troopers Base Defense (Wiz Game)
BitDEFENSE is a Tower Defense game which has a three-dimensional matrix. Goal is to protect the tower from several enemies. Read more about BitDEFENSE (Wiz Game)
At the recently held demoparty Main 2009 ( http://www.mainparty.net/ ) the PoPsY TeAm has released a nice looking demo with 3D effects named "Lack of Disco". Read more about Lack of Disco (NDS Demo)