After a long stretch of burnout caused by great settings backed by terrible games, Anima Prime restored my joy in roleplaying. It hits a rare sweet spot for me between overly-crunchy and overly-handwavey, being a lighter rules set that still gives my mechanics brain something to chew into.

It's also extremely hackable (Creative Commons!) and I've spent way too many hours tinkering with it to aim it in directions it wasn't original intended to go (such as to the setting of Exalted or Pokémon).