Unique Skills

Unique Skills are «Extra Skills» (Weapon Skills with no clear conditions to unlock them) in «Sword Art Online», which differ from regular Extra Skills by the fact that each «Unique Skill» is assigned to only 1 player per skill, while regular Extra Skills have at least 10 users per skill. Just like it is with Extra Skills, the prerequisites for receiving «Unique Skills» are unknown, but they are, apparently, given to the most skilled players. Because these skills are extremely rare, only two players were known to have such skills: Heathcliff had «Holy Sword»; and Kirito had «Dual Blades». Although Sword Skills were later implemented into ALfheim Online, certain suspicious conditional skills, including «Unique Skills», were removed from the system. It is rumored that about 10 skills were removed during verification, which is coincidentally the amount of «Unique Skills» said to have been created.

List of Unique Skills

 * «Dual Blades»
 * «Holy Sword»
 * «Darkness Blade»
 * «Battoujutsu»
 * «Shurikenjutsu»
 * «Infinite Spear»

Trivia

 * The aforementioned «Unique Skills» apart from Dual Blades and Holy Sword were supposed to be unlocked after reaching the 90th floor.
 * Kayaba had stated that Dual Blades was given to the player with the fastest reaction time. The chosen player was supposed to be the hero that would face him at the top of the 100th Floor.
 * Kayaba also stated that there were only ten «Unique Skills» total, in contrast to the "unlimited" number of other skills.