Or Melty Retreat. Buu's Backdash is unique in that he forms into a puddle and drops down while retreating, then reforms back. It's quite nasty, honestly. Holding down during Meltreat will make Buu stay in puddle mode instead of reforming.

Buu turns into half-liquid goo and drops down into a puddle during which his hitbox becomes very small, only low crouching kicks or dropping attacks will be able to connect with him. Hold Down to remain in Puddle Mode. While still holding, you can press Forward or Backward to move yourself into that direction while remaining a blob. Pressing any Punch will make Buu quickly disperse and pop into the air, where he reforms into his humanoid form. From there you can throw out aerial attacks. Releasing Down or (or down-back, or down-forward) at any time will have Buu reshaping into his humanoid form.

Buu solidifies directly into a kicking attack to catch the enemy off-guard. Once it hits, this kick can be cancelled into his Wake Up Call dash attack for a continued assault.

By pressing forward and Medium Punch, Buu stretches his arm for a longer-reaching attack.

Not your average crouching Medium Punch, Buu's version has him making a bit chomp! Preferably to bite into a juicy thigh. It's got one stand-out feature; with proper timing, you're able to eat 1-hit projectiles (with some exceptions) that are being shot at you which also gives you a snippet of health back. Yum!

By pressing forward and Medium Kick, Buu stretches his kicking leg out for a longer-reaching attack.

By pressing forward and Medium Kick while jumping, Buu stretches his kicking leg out a bit farther.

Buu stretches his kicking leg out into the air, for whatever reason!

This can hit overhead on the way up of your jump.

The move's name says it all!

Main tool for launching the opponent, also works as an anti-air attack.

Buu's running attack which can cancel off his Focus Attack. You can also use this out of a Meltdown Kick, in that case the command is just Forward+Strong Punch.

In a totally surprising form of attack, Buu instantly falls asleep in mid-air and falls to the ground, hitting (and knocking down) the opponent with his entire body. If you hold Up while still airborne, Buu will slow down his falling momentum and gracefully float down. You can also steer him to the side by holding Left or Right. Upon hitting the ground, Buu melts into a puddle as he hits the ground and instantly reforms. Holding Down upon landing, Buu will remain in his Puddle Mode.

While not very special in features, its crazy enough to include here. This move is performed by starting out as a cartwheel, but halfway reshaping himself from an upside-down position into upright. It's bonkers! It's a very good move though.

A command attack that hits twice; once when Buu's leg goes up and once more as it comes back down. Knocks the opponent away on the downward kick.

Just like the jumping down+MK, this can hit overhead on the way up of your jump.

Yup, the jumping Strong Kick can do it too.

This aerial version of the Axe Kick can hit three times and knocks the opponent down on the last hit. This guy's got a lot of unique aerial attacks doesn't he?

Buu's main energy projectile is a shoddy sphere that he belches out and which flies in an arc, hitting from above. The Weak punch version has the least range, while the Strong punch version has the most. If the sphere hits the ground, it's destroyed. The EX version is a bit different in that Buu will fire out three projectiles in one belch and they will bounce along the ground until they hit the opponent; all good moves for zoning and keeping pressure on the opponent from afar.

Buu folds himself into a wrecking ball and flies across the screen! After hitting the opponent with it, you're able to chase them with another swoop or move away for hit-and-run tactics. When you swoop downward with one of the follow-ups, Buu can smash on the ground and immediately go into his Puddle Mode if you hold Down.
This this is a sort of Rekka with repeated follow-ups, it has gotten a limiter version; Buu will trap the opponent in a bubble (made of himself) and then smash to the ground. If you hold down after the limiter you stay in Puddle Mode.

Buu rips off his head (don't worry, he instantly regrows a new one) and tosses it onto the ground in a small puddle of Buu goo. Depending on the button strength used to activate the move, after hitting the ground the goo moves either backwards (LP), stays in the center of the screen (MP) or moves to the far side of the screen (SP). It will remain there, lurking. You can't throw out another one of these Gum Heads. By repeating the same command, you can make a Gum Head perform a certain action:
-RDP+LP - The head flies back towards Buu, biting along the way. The opponent can get hit by this guy. The head can even absorb a few hits when returning to Buu.
-RDP+MP - The head bursts up vertically into a slimey pillar of goo, hitting a few times if the opponent is close enough to it.
-RDP+SP - Buu teleports to the head's location to combine with it into a puddle. Holding Down allows him to stay in the puddle.
The EX version of Gum Header is now the Candy Beam (detailed below). You can use a Candy Beam to change a Gum Head into candy, as a fourth option of using them. Eating it refills a bit of your health as well as fills a portion of your Super and (if you're in Hunger Mode) Hunger bar.

Buu shoots an electric current from his antenna that turns the opponent into a piece of candy upon contact with it. The beam doesn't have a lot of range, has a bit of a start-up and is blockable. The opponent remains in this cursed state for a few seconds and is able to move around. Buu can choose to grab and munch on the candy (move detailed below). You can even turn a Gum Head you've thrown onscreen beforehand into a candy and eat it.

Most useful after having turned the opponent into a candy with the Candy Beam. Buu will attempt to grab the candy, and if he succeeds he'll put it in his mouth and munch on it, sustaining damage to the opponent, then spitting it back out which reverts the opponent back to their regular form. The opponent can mash buttons to try to prevent Buu from gaining life, but Buu can mash buttons as well to try and negate that.

A classic Buu move, Buu stomps the ground so hard that his foot burrows through it and pops out of the ground a distance in front of him, with the goal of hitting the opponent and kicking them into the air. The spot where his leg re-emerges from the ground depends on the strenght of the kick button used; Weak Kick is nearby (and best used in your chain combos) while Strong has the greatest range. Medium is inbetween.
Buu now has an EX version of this attack which shoots out three kicks out of the ground in rapid succession. The same general rules apply in terms of distance: LK+MK is the closest to Buu, LK+SK is a bit farther and MK+SK reaches the farthest, full-screen even!

Buu sees your shenanigans, he doesn't like them and as such has decided to blow himself up on contact. This counter can mean trouble if you are not careful. It does only a tiny bit of damage, but you'll definitely have gotten the opponent off you. Hold Down to remain in Puddle Mode.

Buu's got not one, but FOUR taunts! While standing, while crouching (Buu lies down flat on the ground, so it can be used to dodge attacks, mostly projectiles), while jumping (this has a special feature the enables you to stay in the air a little while longer as well as double-jump after the taunt ends) and while performed in Puddle Mode.