ScratchDown is a simple, but interesting little game. Essentially there's a hidden photograph and you can scratch off a predetermined amount to reveal a small portion of it. Then you have to guess, from four multiple choice answers, what the picture is. The less you reveal the more points you get. It's that simple and it's a freebie courtesy of the ad revenue model of pricing.
There's really not much more to say and given that it won't cost you a cent to try I'm not sure there needs to be. This is a game that anyone can play. I'm sure it's the type of game that isn't going to appeal to everyone... but it did appeal to me and seems to be a good social game so that's why I recommend taking a look at it. 4/5 stars because it works well and is free.