With Bangai-O Spirits, Treasure has somehow managed to cram a classic N64 and Dreamcast shooter onto the pocket-sized DS. Even the original's characteristic missile-blossom counterattacks look really badass, despite some graphical slowdown. Spirits features a ton more weapons than the original game and uses a "MIX system" to combine powers.
For example, if you select Napalm and Break, you'll get the explosion of a Napalm missile without the penetration penalty, so you can shoot through enemy bullets. Hitting the B and Y buttons (or L and R, in the case of EX moves) simultaneously allows you to fire each weapon separately. Not all weapons can be mixed, but the sword, bat, and other nonmixable weapons still have their place in combat.