Sex kick

Mario's sex kick in Brawl.

A "sex kick" is an aerial attack in which a foot or arm remains extended for a few moments after the initial thrust. The term was coined by smasher Matt Deezie as a sexual innuendo referring to the properties of the attack in the original Super Smash Bros. A visual sex kick consists of the thrust (kicking motion) and the extension (leg remaining out), with the other leg bent and the foot tucked beneath the kicking leg's thigh. Sex kick mechanics in more recent games include attacks that do not resemble kicks and are no longer exclusive to aerials.

Properties

Properties of sex kicks include:

A single hit.
Predominantly sideways knockback.
A long hitbox duration, with lower damage and knockback after its first few frames.
Fast startup and low landing lag.
Similar animation and hitbox placement throughout the entire attack.

These properties make sex kicks very useful in the neutral game and escaping combos and pressure, at the cost of having limited utility in the wielder's own if not performed close to the ground.

Sex kicks are almost always a neutral aerial, and the term classically refers only to neutral aerials. However, some characters wield other attacks — most commonly back aerial — that exhibit similar properties, and smashers often refer to them as sex kicks.

Notable sex kicks

Luigi's neutral air from Melee onward deals vertical knockback on both the clean and late hits. This allows him to set up various combos into other moves, including his Super Jump Punch's sweet spot. It is even capable of killing at reasonably high percents.
Dr. Mario's neutral air reverses the typical properties of sex kick hitboxes: the initial hit deals lower knockback than the lingering hitbox, making it more effective for edgeguarding while changing the range in which it can combo.
Samus's neutral air in Melee possesses exceptional range, which helps it combo. This gives her a strong way to knock characters offstage and set up an opportunity for edgeguarding, where the exceptional range on her neutral air once again proves useful.
Fox's and Falco's high falling speeds allow them to quickly follow up SHFFL'd neutral airs and back airs in Melee. This allows for incredible shield pressure, as well as combo options off of a later hit. Moreover, their back airs have impressive knockback on the first few frames, making them a strong way to end combos.

List of sex kicks

Super Smash Bros.

Pikachu performing a sex kick in Smash 64.

Most characters in SSB have one sex kick: their neutral aerial. The two exceptions are Donkey Kong, whose sex kick is his back aerial, and Fox, whose neutral and back aerial are both sex kicks, making Fox the only character with two sex kicks.

Super Smash Bros. Melee

Captain Falcon - Knee Smash
Dr. Mario - Neutral aerial
Falco - Neutral aerial, back aerial
Fox - Neutral aerial, back aerial
Jigglypuff - Neutral aerial
Kirby - Back aerial
Link - Neutral aerial
Luigi - Neutral aerial
Mario - Neutral aerial
Samus - Neutral aerial, Back aerial
Sheik - Neutral aerial
Yoshi - Neutral aerial
Young Link - Neutral aerial

Super Smash Bros. Brawl

Captain Falcon - Knee Smash
Falco - Back aerial
Fox - Neutral aerial
Jigglypuff - Neutral aerial
King Dedede - Neutral aerial, back aerial. His back aerial is considered by many the best sex kick in Brawl, due to its damage, speed, range, and duration.
Kirby - Back aerial
Link - Neutral aerial
Luigi - Neutral aerial. Unique in being the only sex kick with vertical knockback.
Mario - Neutral aerial
Samus - Neutral aerial
Sheik - Neutral aerial, back aerial
Snake - Back aerial
Yoshi - Neutral aerial
Zero Suit Samus - Flip Jump kick, making this the only special move in Brawl to be a sex kick.
Mites sometimes sex kick the player.