Depending on how much you want to spend, you can potentially get a bunch of collectibles with your copy of Disgaea 4: A Promise Unforgotten.
I mean, the standard edition of the game is only $49.99, so you can already buy the game for $10 less than most games. But for $59.99, the premium edition can be yours, which adds a special box, a figurine of the character Fuka, and a softbound artbook. If you sleep on a pile of money, there is also a premium figure edition that includes all the stuff from the premium edition in addition to nine additional figures to decorate your shelves with.
If you're only getting the standard edition, you don't have to be left out of the goodie giveaway. Any pre-orders through NIS America's website include a free soundtrack CD, which should indicate the place you should be ordering Disgaea 4 from. Pre-orders last until September 5, the day before the game's release, but as always, I recommend ordering early in case the freebies run out.