PvP in Doomed.io is a highlight of the game once you've mastered not dying in the night. Currently it is advisable to set up a base with turrets so that you have somewhere to return to once combat ensues or you need a reprieve. There are various weapons used during this time but as of v1.1 popular methods have been using the Cross bow or the Crowsbar as they have a piercing effect against players in armor.
A new feature recently added allows the top player of the server to announce his position on the map. This acts as a challenge for other players to "dethrone" him to take the title for themselves. Top players will have a crown next to their names and can be seen on the leader board in 1st place on top right.
Killing a player awards large amounts of exp as well. Higher level players will give substantially more exp upon successfully striking the last blow during combat with them. Additionally upon killing a player all their items will be dropped and lootable.