Forget that announcement saying it would be out on March 19. It's not. It's out today, so if Metal Gear-themed Duck Hunt sounds appealing, get on it.
It's US$8, it features characters and settings from Metal Gear Solid 4, and it clocks in at an impressive 90MB, so you'll probably want to download it via your PC/Mac first. No demo or "Lite" version, sadly, so the video below is as good a taste as you'll get without parting with $8.