The Strife Specibus fistkind is used by a few characters in Homestuck, most notably by Equius Zahhak. As the name suggests, it involves the user attacking with their fists. Many players have been shown punching enemies and other players without Fistkind, so it can be assumed that this specibus amplifies the user's hand to hand ability.
Roxy Lalonde is also with a fistkind specibus in her Strife Portfolio, and she is seen using it during Collide. Her pre-scratch counterpart in was seen beating an enormous monster from LOLAR with only her fists as well.
Hussie suggests in the author commentary of Homestuck: Book 4: Act 5 Act 1 that there is "...something to be said for Void players being naturally inclined toward fighting empty-handed," as Equius and Roxy "naturally" have it allocated.