It's not the most complicated fighting action in the world, but Photo Dojo for DSi is a pretty cool little toy. The premise is that you can take pictures of yourself, or your friends... or maybe even your cat... and place them into a side-scrolling brawler. You'll take photos for the game's different frames, such as a kick, a punch, a fireball motion, the actual image of your projectile, and so on. The animation is, well, incredibly crude. And you're really just sort of placing photos into preset shapes, so it's not like your body shape is building hitboxes or anything complicated like that.
But that's not the point. It's meant to be goofy fun. The controls are also incredibly simple, using one button and the D pad for most moves. So hitting back and a button will toss fireballs, down and a button does another special move, forward and the button punches, and so on.
Going through the fighter creation process was one of the first things I did at Nintendo's event yesterday. Since you can create multiple fighters and store them, I remained on the cart for awhile. Or at least long enough to apparently murder Destructoid's Dale North, as piloted by Nick Chester.
UPDATE: Brian Ekberg beat me up. Just like I always knew he would.