Why can't I make Killer Bunny spawners and Ender Dragon spawners?
Solution 1:
Extra entity data goes inside the SpawnData compound. The correct tag name is RabbitType rather than Type. Tags are separated with commas.
Fixed command for 1.8:
/setblock ~ ~ ~ minecraft:mob_spawner 0 replace {EntityId:Rabbit,SpawnData:{RabbitType:99}}
Fixed command for 1.9, where EntityId no longer exists and the ID is instead defined by the id tag inside of SpawnData:
/setblock ~ ~ ~ minecraft:mob_spawner 0 replace {SpawnData:{id:Rabbit,RabbitType:99}}