The outstanding Codemasters racing sim Grid is on sale at GOG (as Race Driver: Grid) for a mere $3, which while not as good a deal as the recent Humble freebie is still awfully cheap. But if you're tempted by the price, you'll want to move on it quickly, because the game is scheduled to be removed from GOG's lineup at 6 pm ET on December 31.
GOG didn't provide a specific reason for Grid's removal, but confirmed in an email that it's being pulled because of expiring licenses. It's unfortunate, but it happens from time to time: The Fallout catalog was removed at the end of 2013, and Duke Nukem and Descent were pulled in 2015. The Fallout games have since been returned, and it's possible that Grid will eventually make a comeback too; on the other hand, Duke and Descent are still MIA, so you might not want to hold your breath.
However it ultimately works out, the good news is that Grid owners will not be affected by the removal. It's yours to keep forever, as long as you pick it up before the deadline.
Update: It's always a good idea to back up your stuff, but as several commenters have pointed out, Grid owners will still be able to download it from GOG after its removal from the store—it simply won't be available for purchase any longer.