Most favorite... probably tillering, though its a love/hate thing, especially if its a snakey stave. I also love the smell of freshly worked osage.
Least favorite is trying to sand a bow to a perfect surface before applying a finish. Its mainly cosmetic, many people don't bother and I can understand why. It doesn't make a bow shoot any better, its very time consuming, but it sure looks nice. Despite my reservations I always seem to put the work in to make sure the finishing is flawless.