While the new Smash games don't have the famous technique from Melee that players called wavedashing, they do have something called "perfect pivoting" — and it's similar/useful enough that you'll want to learn how to do it if you're playing seriously.
My Smash Corner explains how to do the technique in this video, and why it's worth doing in matches. Basically, when you dash in one direction, then flick your stick in the opposite direction, your character will do something like this:
Why would you want to do that? Well, it's a good way to fake out your opponent for one. Second, it's a good way of controlling space. Third, perfect pivoting allows you to perform quick, safe attacks that are difficult to protect against if your opponent isn't knowledgeable about the technique. You can also use it to punish, to grab opponents quickly, and much more. You should learn it, if you can!
Perfect pivot length can vary from character to character, and My Smash Corner breaks that information down in the video. Do note that, while this is a technique on the 3DS too, the fact there's no C-Stick there means its uses are a tad more limited — never mind the fact that flicking very well might destroy your circlepad. Be careful!
Perfect Pivoting! (Smash Wii U/3DS) [My Smash Corner]