I wont say anything about the best move, but I can tell that U-tilt, B-air, The Arrow, and the Mirror Shield are my favorite moves.
U-tilt: Look at how it's performed. 1 side of the bow on the ground, and Pit does a double kick upwards. It is so amazing, and it does more damage than the Usmash.
B-air: It's the killing move when you sweetspot it. Uses his feet to kick in front of him to add to the force of him stabbing behind him. Such a powerful move, for the angel.
B (Arrows): The one projectile with the most mindgames. Seeing how you can control it, loop it, rain it, the tech for such an arrow, I love it. It has KOed many opponents, yes, the arrow itself. Arrow star KOs, and everything. Sorry Link, but angel arrow technology is superior to yours.
Mirror Shield: It's a reflector that has special properties. Certain projectiles like Lucario's Aura Sphere, Samus' Charged laser, and Wolf's blaster, when reflected, return back at a faster speed than normal, while at the same time, being able to do more damage. It acts like mario's cape at the shiny sound, which reverses oppoents who hit the shield at the shiny moment, and can gimp many recoveries, like Link's and Ike's at the right time.
"Nice try!"