These people are brave enough to do this, but sometimes courage borders on insanity.
Swiss extreme skier Jeremie Heitz, 27, is seen here plummeting down the near-vertical 4,000 m (13,000 ft) drop at terrifying speeds in the Pennine Alps. Jeremie took on the challenge while filming an eye-popping video for Red Bull.
Warning: don't try to do it yourself!
They even stand up on the rear wheels.
This Japanese guy didn't go to the dentist in 10 years, combine that with poor dental hygiene (no flossing) and this is the result.
Only one, but it's no easy task.