1. My favorite Indie Game is either Mark of the Ninja or Hotline Miami both very very good games, least favorite is probably Dear Esther.
2. Weirdly the developer is usually what makes me want to play it the most for example I just finished watching Indie Game: The Movie on Netflix yesterday and now have bought Super Meat Boy and Fez
3. Gonna have to be controls, trying to play Rouge Legacy without an Xbox controller requires at least 7 hands and 8 fingers on each hand.
4. I like difficulty so I think platformers work best for this again I would point at Mark of the Ninja which can get very difficult if you're trying to play without murderizing everyone.
5. I tried making a game a few years ago involving pigs, mirrors and lasers but work caught up with me and never completed it, my current project is above top secret ;)