Oftentimes, if I need to fall asleep I'll pick a really peaceful one. When I was younger, I had one where I was a full sized person in a world made entirely of legos, including tiny living lego people. I'd fall asleep, dreaming of building secret tunnels under the ocean, vast cities with towers a mile high, train tracks for the lego people that climbed mountains that rose above breathable atmosphere to reach secret veins of special legos. It was only during the day that floods, earthquakes and rival lego people threatened.

On a related note, I have such awesome ideas for a Minecraft mod.