Yoyo glitch (Brawl)
This is a commonly talked about glitch which leaves Ness's Yoyo out. When preformed, his Yoyo will hang from his hand and he can still attack, taunt etc. It can only be performed in Super Smash Bros. Brawl.
How to preform
First, both a Ness and a Lucario are needed. A flat stage such as Final Destination is best, but any stage can be used. Using Lucario, get a fully charged aura sphere. Shoot the aura sphere at Ness, then have Ness do his up smash. If done correctly, the aura sphere should pass Ness's Yoyo and hit him, thus canceling the animation of him putting away his Yoyo. If Ness passes through a platform, then the Yoyo will be "caught" and will appear to be stuck on the platform. It will automatically go back to Ness if it finds a clear line between it and Ness. If Ness gets KO'd, then the Yoyo will be stuck under the stage. It can still go back to Ness if he finds a clear path between himself and the Yoyo.
The glitch was discovered by Henpen924. [1]
Video
Below is a video explaining the glitch and how it works.