I recently found something very fun do with the new and improved Extreme Speed: Sudden Death
I was doing some matches against my roommate shortly after we first got the game. At one point we were put into Sudden Death since we were both down to one stock after the timer ran out. For a few tense moments I started thinking about how I was going to approach the situation, coming up with stratagems and postulating tactical maneuvers to land that all-important killing blow.
Then, suddenly, I remembered that I was playing with Smash4 Lucario.
Newly armed with my realization, when the announcer's voice screamed "Go!" I immediately initiated an Extreme Speed toward my enemy. Before the the word "Go!" had even faded from the screen, it was promptly replaced with "Game!" and Lucario's win music began playing in my headphones.
So it turns out, on Omega form stages 1v1 at least, the characters are spaced at just the right distance for Lucario's full-aura Extreme Speed to drop the hitbox right on the opponent's spawn point. Of course in Sudden Death, both characters are at 300% damage... I think you get the idea.
After that match, every single time I have been taken to Sudden Death using Lucario, I've done the exact same thing, and it's won me Sudden Death every single time except for once, and that was only because I angled the circle pad up just a tiny tiny bit, which sent Lucario sailing off the other side of the stage to his demise (oops!). I know it won't work if the opponent knows to expect it, but damned if it ain't satisfying when you catch the other guy totally off-guard like that!