List of techniques used by Skull

Physical Abilities

 * Soul Crusher: A technique seen in the second episode of the anime and second chapter of the book, as well as some of the video games. Skull used this against Genocide Error during their battle after gaining Geno Error's wires. Skull punches the opponent into the air and then jumps into the air before elbowing them hard in the head and knocks them to the ground, he will then drop to the ground and stomp on the opponent's head. Named in FightZone, alternately named Hacker's Death Drop in Victory Battle as the Ultimate technique for Skull (Hacker), Also called Slam Dunk in Undertale Unofficial Fighting Game

Magic Abilites

 * Energy Blast: The most basic form of magic manipulation where one throws a blast of energy from one's hand at the opponent.
 * Fake Blast: A trick used by Skull against Geno Error where after throwing his hand forward a bunch of confetti comes from his hand, confusing the opponent, used to disorient Geno Error during their battle.
 * Coding Control: Early in the series and now currently, Skull has shown to have control over the coding of the game to make anything he needs.
 * Portal Walking: used to trail Error to his home during the first episode of the anime.
 * Character Coding Control: used to change specific aspects of a person, such as gender, height or race.
 * Shapeshifting: Skull can change his look to match anything he wants, most commonly used to turn into a small cat for EC's Comfort 
 * Move Copying: Early in the series and supposedly at current, Skull can copy moves he's seen from other people and use them to his advantage
 * Pyromancy: Never explicitly shown but it was mentioned that he used pyromancy to burn down the skull in the first episode, copied from Toriel
 * Bone Manipulation: Skull can control bones to use for his own purposes, shown very early on, mainly used as an attacking weapon, copied from Papyrus
 * Psychokinesis: Skull can lift people up by the soul and throw them around with psychich powers, copied from Sans
 * Spear Control: Skull can telepathically use long blue spears for attacking, though he never uses them for the intended purpose. copied from Undyne
 * Trident Control: Similar to Spears, Skull can telepathically use large red tridents in battle, usually to attack opponents, copied from Asgore
 * Gaster Blaster: Skull can summon a large skull like creature to fire forth an energy beam from it's mouth, causing damage, copied from Sans
 * Error Wires: Skull can summon up long wires that can be imbued with electric shocks mid battle, copied from Geno Error.
 * Gaster Cannon: Blackjack's signature technique, Skull points his hand forward and summons energy around it before condensing it into a small ball before firing a wave of energy, shown in several games including Skull's Striped Shirt 3, Jacket 2 and Battle Outfit 4 presets in FightZone's Adventure Mode. Also shown rather quickly during a training session with Jack.