2. Every FPS ever – Teabagging.
This war crime finds itself so high up the list because it is both universal and unending. The practice of crouching and standing over the body of an enemy to imitate shoving your balls in their face is, at the very least, a flagrant violation of the protections given by the Geneva Convention to the bodies of enemies, which must be treated honourably and not defiled. At worst, such conduct may amount to fictional war rape, which is defined by modern amendments to the Conventions as a crime against humanity. While the objection can be raised that the victims are already dead when this act is performed, I would point out that kill cams and respawn mechanics allow them to experience it as if they were alive – which is, indeed, the point of doing it in the first place.