Dash attack canceled up smash
Dash attack canceled up smash (DACUS) is an advanced technique in Brawl that is performed by initiating a dash attack with the C-Stick and immediately afterward performing an up-smash command, alternately achieved with either the Z button or the traditional Control Stick method. Any character can do it, but only certain characters gain a noteworthy addition to their attack strategies because of it. It is also commonly referred to as "Boost Smashing."
Uses
A DACUS is useful when the character physics behind it allow the up-smash to slide significantly far and fast across the stage while charging. It adds an extra factor to a character's KO potential, or can simply be used to surprise a distant opponent in the interest of maintaining close quarters. With good timing, it is possible for both the initial hit of the dash attack and the up-smash to connect, providing extra damage.
Characters
This is a short list of characters that have a sliding DACUS:
1. Snake: The most useful Boost Smash for stage control, as well as the easiest one to connect both the dash attack and the up-smash (the initial hit, at least). A well-known maneuver for any advanced Snake player, as its speed and range are excellent at both interrupting and launching yet another explosive into the battleground.
2. Sheik: The most useful Boost Smash for killing, as Shiek's up-smash is her strongest killing move, but is unfortunately difficult to sweetspot under normal, stationary circumstances. It is one of the more difficult Boost Smashes as far as timing goes, but it is also tied with Snake's for being the farthest and fastest.
3. Link: Useful in its ability to make the normally-slow Link move much faster while attacking, and excellent when combined with Link's strong projectile game.
4. Jigglypuff: Like Link, Jigglypuff's DACUS assists her slow ground game by giving her this sliding smash.
5. Falco: Falco's best DACUS will slide halfway across Final Destination, and gives him yet another follow-up option to consider after connecting with a canceled Blaster shot or his down-throw. Falco can also easily chain the actual dash attack into the up-smash, although it can be performed with a different set of commands (A while dashing, up on C-Stick upon first few frames if a hit is landed) and will not slide.
6. Wolf: Wolf's DACUS gives him two sliding smashes, as opposed to just forward-smash. This one, however, is significantly more powerful.
7. Pit: Pit's DACUS won't always catch the opponent in the final hit, but it's useful as a speedy interception tactic.
Squirtle's sliding smashes
Squirtle is unique in that he can slide all three of his smashes quickly across most of a stage's length; however, he does not use the DACUS command to accomplish this (see Shellshifting).