The Ender Dragon takes damage from the normally non-harmful Fishing Rod and Eggs.
Steps to Reproduce:
1. Make a new Creative world.
2. Construct an End Portal and enter it.
3. Get a Fishing Rod and Egg from the Creative inventory.
4. Destroy all of the Ender Crystals.
4. When the dragon approches you, attack it repeatedly with both and notice it takes damage.