It's been a while since we've seen the first 2D games making use of physic engines, but here is the first one which I'd really like to play with. PixelJunk Shooter is a game available on PS3 Network, and is both a platform/action and a puzzle game (kind of). From what I've seen, you control a ship to rescue PNJ scattered in a 2D world.

According to the level, you're surrounded either by fire or ice, and need to use the available resources to make a way to the exit. You can drop water on the fire, or fire on the ice, each fluid being rendered with a smooth animation. An image being better than a thousand words, I'll let you enjoy the video.

PixelJunk™ Shooter E3 Trailer [Youtube]

Well, if crime fighters fight crime and fire fighters fight fire, what do freedom fighters fight? They never mention that part to us, do they?

George Carlin