Neat topic!

Five experiences come to mind when I think of the coolest things I've ever done in a lucid dream.

In no specific order:

1. I flew into outer space and circled around the Earth.
2. I dream spun into a whole new, uninhabited world and explored via flight. I saw the most amazing landscapes...
3. I made another planet collide with Earth.
4. I went Matrix style on an army of ninjas.
5. I flew to the middle of the ocean and created a giant whirlpool. I flew right into it but woke up immediately after.