1) Be able to mine clouds
I've noticed you can mine pretty much anything, but what about those fluffy clouds you see in the sky? It could have
a negative affect on gravity, so you could make a kind of "Castle In the Sky"-esqe shelter.
2) Create a bat monster that only appears in darkness, any kind of light source scares it away.
What's scarier than having to watch your back? Getting attacked from any side, even from straight above. Hitting
it would require some patience and skill.