The Rufio is a famous Meta Knight combo, and is a staple of his metagame in both Super Smash Bros. Brawl and Super Smash Bros. 4, particularly in Brawl. The combo consists of Meta Knight chaining his Up aerial into itself multiple times and finally KOing the opponent with either a Mach Tornado or Shuttle Loop. The number of up aerials varies, but is usually either five or six, depending on the opponent's weight, fall speed, and size.
The origin of the term "Rufio" is unknown.
The Rufio made its debut in Brawl. Meta Knight's up aerial is among the fastest moves in the game, with its hitbox coming out on frame 2, and it also features interruptibility on frame 13, allowing Meta Knight to potentially perform three up aerials in a single short hop. It also has a disjointed hitbox, low damage (6%), and weak knockback (40 base/125 growth). All of these traits make it a superb combo tool; Meta Knight's five midair jumps can also allow him to easily and quickly pursue opponents in the air when he uses the attack.
The Rufio is generally started with a dash attack, as it sends opponents in the air and into the upcoming up aerial's path. A number of options also exist to allow Meta Knight to combo directly into his dash attack, including his down tilt, due to its deceptive range and tripping potential, as well as auto-canceled forward or neutral aerials at low percentages. Alternatively, Meta Knight can use his down throw, but this can be DIed and air dodged out of.
Upon sending opponents into the air, Meta Knight needs to immediately jump and begin using his up aerial to combo his opponent into itself, jumping when necessary in order to get the opponent closer to the upper blast line. When Meta Knight has used all of his jumps, he can then finish the combo either by using Shuttle Loop or Mach Tornado. The Mach Tornado finish is generally considered easier to perform, as it does not require as precise of positioning and it sends opponents upwards when the move is completed. The Shuttle Loop finish, however, is considerably more powerful when it lands, and as the move transitions into a glide, it is much safer if it whiffs compared to Mach Tornado, which makes Meta Knight helpless instead; however, Shuttle Loop sends opponents at a semi-spike angle, generally making it more useful if the opponent is close to the left or right blast lines.
In Smash 4
Meta Knight's up aerial was nerfed from Brawl to Smash 4, with its start-up increasing to 5 frames, and its interruptibility now occurring on frame 27, about twice as much as in Brawl. Furthermore, it deals 1% less damage (6% → 5%) and weaker base knockback (40 → 30), alongside having greater knockback growth (125 → 128). The later 1.1.5 update further nerfed the attack by giving it a more horizontal launch angle, and increased its SDI multiplier, making it more difficult to combo into itself. Despite these nerfs, it still commands a rather high range, especially given the other nerfs to Meta Knight's disjointed hitboxes, and Meta Knight's increased air speed also makes it more difficult to DI out of his up aerial, alongside the removal of hitstun cancelling. Overall, the Rufio is less effective in Smash 4, owing to a smaller pool of characters it can be reliably performed on; the Rufio is now only guaranteed on floaty lightweights, such as Rosalina & Luma and Kirby, and against other characters, it is generally only effective for racking up damage.
Meta Knight still has reliable set-ups into the Rufio. His dash attack deals more knockback (40 base/88 growth → 70 base/90 growth, and is now disjointed), and while his down tilt has shorter reach, it is still quick and safe, and it can still trip opponents. With the aforementioned removal of hitstun cancelling, both his down and forward throws can also lead into the Rufio, although the latter is escapable via DI, and the former is completely guaranteed only against heavyweights and fast-fallers.
In Smash 4, the Rufio is generally finished with Shuttle Loop only. Despite buffs to Mach Tornado's knockback, its shorter duration makes it risky to use, and the attack's momentum was also nerfed between games. While Shuttle Loop no longer cancels into a glide, it deals more damage, has high knockback growth, and inflicts vertical knockback, making it especially deadly when used near the upper blast line.
The Rufio can be used to zero-death opponents susceptible to the Rufio by exploiting the changes to Meta Knight's back aerial. His back aerial now uses the autolink angle and as a result, Meta Knight can dash attack and follow-up with a back aerial, and then fast-fall and land before the final hit. If the opponent does not tech, he can jab lock them with his down tilt. As they are forced into their neutral get-up animations, he can land a dash attack, grab, or up tilt, and then start the up aerial chain, and finish with a Shuttle Loop, KOing if executed properly.
Alternatively, Meta Knight can dash attack into an up aerial and then footstool the opponent, preventing them teching the resultant knockback and creating an inescapable zero-death. Interestingly, this zero-death works on all characters except for heavyweights, such as Donkey Kong. After the back aerial, they only flinch rather than fall over, and when footstooled, Meta Knight cannot reach the ground fast enough to start the jab lock.