Turn Kirby into a Raging Fire Ball
Via Kotaku:
Here's a how-to on the exploit:
The “Fire Kirby” exploit was first found by Swedish Smash player Enis Al-Maatooq, the guy who previously discovered a nifty and highly technical way to reduce character lag in the latestSmash Bros. He told me that he poked around with Fire Kirby to see if the exploit had any similarly game-changing consequences, but didn’t find any...yet.
Here's a how-to on the exploit: