Kirby (SSB)/Up tilt
Kirby does a vertical kick. It is widely regarded as among the best attacks in the game, and maybe even the series, due to dealing high damage and knockback (14% during its first two frames and 10% for the rest of its durtion), quick speed (hitting on frame 4 and being only 17 frames long, which is extremely fast and hard to counter) and its notably disjointed hitbox that covers the length of more than one Kirby both horizontally and vertically. These traits give the move excellent combo potential. It can easily chain into itself at lower percents (which can deal up to 70%+ depending on the weight and falling speed of the opponent) and at higher percents, it can easily lead into other moves such as back air or neutral air and it can lead to kill confirms; especially the late hit. The late hit can also lead into the clean hit (via pivot) at mid to high percents.
The move's extreme speed and high damage also give up tilt incredible shield pressuring potential. A fresh, clean up tilt leaves Kirby at +12/+13 frames (depending on if it hits on frame 4 or 5) against a shielding opponent while the late hit leaves him at anywhere from +8 to +13 depending on when it lands. Because of this, Kirby can very easily chain up tilts against a shielding opponent (who cannot do anything to avoid it) which can then lead into a forward smash for a shield break combo. However if the move is fully stale, it is only +7/+8 on shield (+3 - +8 for the late hit); which removes the move's ability to lead into a forward smash (although if the opponent is close enough, they cannot roll or jump quickly enough to avoid the forward smash if the clean hit lands, forcing them to take the hit either on hit or shield unless they have an intangible up special out of shield).
This move was considered to be the main reason Kirby hard countered fast fallers and heavyweights such as Captain Falcon and Fox as it leads to early easy edgeguards when combined with aerials. This also lends to Kirby having the strongest matchup in the game against Yoshi along with Captain Falcon although in the current metagame, Kirby's matchups against these characters aren't as strong as once thought due to advancements in their metagames. Along with back air and down air, these moves are the primary moves in Kirby's arsenal especially when combined with pivots.