I was able to get a look at the Maverick that they are giving away as a doorbuster at GameStop, as well as get some info about how it will work. I have some friends that work for GS.
First off, here is a pic of the Maverick:
OMC is right that you will only get it if you buy the N-Strike Game bundle for the Wii priced at $59.99. Each store has about 12-24 Mavericks. The store I went to is a high traffic store and they only got 12 in for tomorrow. There is a major catch to the doorbuster to ensure that people don't abuse the sale. Anyone out there that may have thought about buying the bundle to get the Maverick and then returning the bundle will have their hopes crushed. If you return the bundle, you must return te Maverick as well. They will not take the return at all (not even for store credit) without seeing the receipt and receiving the Maverick in an unopened package. If the package has been opened in any way, they will not accept the return and you are stuck with it and the game you may not have wanted.
Good luck getting one. I'll be in line at 4 AM just for this.