Mine changes with the weather it seems, but currently;
#1 - Volley - It challenges my entire skillset, from getting the damn plunge through the top lanes, trying to hit one drop at a time, flipper skills, nudging, tilt ends game, etc. It's always a challenge and has really helped me build my skills.
#2 - Ali - Because the damn thing kicks my ass every time, but when you actually build a 5x bonus and collect it in the scoop, the bonus burn is awesome. Even when you make a shot, the ball is completely out of control.
#3 - BM66 - There is always something different to do and so many ways to attack the game.