Minecraft wiki entry for Development_versions, associated text: Armor stands
Version exclusive: Can stack up to 64
Book and quill
Version exclusive: Can hold two pages at the same screen
Version exclusive: Edit button to change the words per page
Firework star
Firework rocket
Version exclusive: Can be launched in any direction depending on the direction a dispenser is facing
Music discs
Spawn eggs
Parrot
Zombie Villager