Strata - A puzzle game I found on Desura a while back. Simple and lovely, with a basic premise - lay down the coloured ribbons in sequence so that the right colour is the last one over each corresponding square. It struck me as a perfect game for tablets, so I'm am glad to see they recently announced that it will be coming out as an app as well.

It's been on sale half-off a couple times, so you can wait to see if it does again before buying. But either way, if you like puzzle games I recommend this one.