Dare you to walk in the Graveyard at night!
I dare you to hug the next person you see!
Dare you to log off?
I dare you to grow up...
Drink gasoline, but not enough to kill you. Drink some oil, too.
Post a video to youtube, and prove it's you. Like, state in the video "I am grasshopper831" and then drink gasoline and oil, and give us the link to the video.
How will we know you completed it?
Humm.. I dare you to go find and obtain a job that you are not qualified for.