If you don't already know, it's known as controller default.
To get your character in SSBB to jumping off the ledge in a stage where there are no walls on the sides (by running off in one direction automatically), follow these simple steps :
Unplug your nunchuck from your Wii Remote
Tilt the nunchuck control pad in any direction other than neutral (up, down, right, left). Your character will go in the opposite direction as this (right becomes left, up becomes down, etc.).
While tilting the control pad plug the nunchuck into the Wii Remote with your other hand. You can grab part of the remote with part of your hand used to hold the nunchuck.
Now your character will go in the opposite direction as you put the control pad in step 2.
Here is a video I found which illustrates the stage in the "Tips" section below.
Tips
To suicide faster, use a map with only two large-sized falling blocks on the sides and go to Special Brawl. Choose mega, fast, 300% damage, and metal then use Bowser or Ganondorf (all the characters' walking speeds are actually almost the exact same! Sonic may appear to walk much faster than Ganondorf but Ganondorf has longer legs ^^, same with all the other characters.
