Duck Damage in Gas Filled Rooms:
Roll around the room by holding the right trigger and using the left joystick to move Batman around the room non-stop.

Get All the Stuff:
Spoiler Alert! Beat the game once on any difficulty and you will get: Every move, interview, the enitire Gallery of Fear, 2 Batmobile Missions, and three costumes. Which are: The World's Greatest Detective, Caped Crusader, and Dark Knight.