I found a bug that gives you invincibility for about 5 seconds on a single player world. It allows you to fall of a cliff or something similar without dying. You could even survive lava! If you re-log into the game it will give you a bit of invincibility. To see it in action, please watch my video I made about it: https://www.youtube.com/watch?v=S_c7Gj7Kv0M

What I expected to happen was...:
I would die.

What actually happened was...:
I didn't die.