Banana Peel

The banana peel is an item from the Mario Kart franchise. It's randomly obtained by running through one of several item boxes, that lies scattered throughout each stage. The resulting item may vary depending on the players position in the race. It is more likely the item will be a banana if the player is in the lead.

Different Uses

The banana peel can be thrown in two direction; forward and backwards. 

Backwards

If the player choose to throw a banana peel backwards, it can pose a threat to all racers currently behind. A strategically placed banana peel can really muck up for potential race winners as they try to regain control of their vehicles. 
If someone is riding up very close to your bumper, the best way to get rid of him is to drop a banana peel, then watch and laugh as your opponent spins out of control. 

Forwards 

Sometimes, the player is unlucky enough to receive a banana peel while not in first place. 
However, a skillful driver can still put the peel to good use. By pressing a certain combination of buttons (depends on game), your can toss your banana peel in front of you. It takes precision aim to throw the banana peel right, but if done correctly it is possible to make the banana peel land in the path of the driver in front of you. Be careful to not run over one your own banana peels as your drive forward though. That would just be plain embarrassing. 

Effects of Banana

The banana can cause short term as well as long term effects by anyone who happens to run into one. 

Short term

Hitting a banana makes you spin out. You may lose a couple places in the race, but nothing that totally ends your chances. That's if you get hit with one at the beginning of a race. 

Long Term

Running into Banana has proved to really take a mental toll on players. Cases of controller throwing because of running into this fateful item have been reported. There is nothing more frustrating then being in a solid second place, only to run into a yellow friendly looking banana, and lose multiple places. 

Other long term effects may be spending hours pondering how a single banana can cause a go-cart to entirely lose control and spin out. Many have tried to duplicate this, but all have failed. It must just be a secret of the Mario world.