My first download was Pocket Frogs, and the first game I paid for (and this is embarrassing) was EA's Surviving High School. A bit later on I downloaded Doodle God, Pocket God, and The Quest Gold.
First game I bought was Slay. I stumbled upon it and remembered playing it on the PC yeeears ago. Quite excited seeing as how I had always wanted to buy the full version for the PC, this worked out even better!