Slide Smash
Slide Smashing, also known as Smash Dashing or Hyphen Smashing is a simple, but useful technique. To do it, simply dash and use an Up smash; your character will slide to a stop while performing their Up-Smash. All characters can Slide Smash.
Application
The most obvious use for the Slide Smash is as an alternative to using the character's dash attack, which is generally mediocre to weak in terms of power; many dash attacks also leave your character vulnerable where as the Slide Smash is generally difficult to punish. Another use is simply as a set-up to an Up-Smash, which can be used to combo or to kill. Finally, for fast characters such as Sonic, Captain Falcon and Marth a Slide Smash covers incredible distance, which is useful for approach.
See Also
DACUS, a very similar technique with the addition of a canceled dash attack