Every month, there's a new, exclusive mini that you can pick up at your local GW store. This month, it's a new Grey Knight figure for 40k.
From the article:
Not only can you pick up the coin and collector’s album, the Miniature of the Month is none other than a powerful Grey Knights Strike Squad model. The miniature is available while stocks last, so ask your Warhammer shop how to get one. Use it to test out a new colour scheme, paint up as a special project, or even add to your growing Grey Knights army.