The main RuneScape Wiki has an article on: Player killers
The Old School RuneScape Wiki also has an article on Player killers.

Player killers (or Pkers) are players that fight other players with the intent of either gaining rewards or just for fun. The act of killing another player is known as PKing. In RuneScape Classic, PKing takes place in either duels or the Wilderness. Keep in mind that in the Wilderness, dying will cause a player to lose all but their three most valuable items. In a duel you may risk items if you want, but it isn't necessary. Most Pkers tend to use a rune two-handed sword. Formerly, Wilderness-style PKing took place all over RuneScape, but this feature was later removed.

Community content is available under CC-BY-SA unless otherwise noted.