The freedom the Arcade gives the Overwatch team has allowed them to add Deathmatch - coming soon to Overwatch. Free-for-all Deathmatch will be you against seven other players.
In Blizzard's newest now expected developer update for Overwatch Jeff Kaplan tells us all about Deathmatch and the changes it brings with it. This update including Deathmatch is available for testing on the PTR.
In The Arcade you will be able to join a Deathmatch or Team Deathmatch mode. Free-for all Deathmatch comes with a new map, Chateau Guillard. This chateau will contain hints to Widowmaker's backstory given that before marriage her name was Amelie Guillard - Chateau Guillard is her families estate in France.
For Team Deathmatch the arena maps will be used as well as modified capture the flag maps. Jeff makes a special mention that Mercy's resurrect takes kill credit away from the enemy team when used. Free-for-all players receive a win credit in the Arcade if they make it into the top half of the scoreboard, or the top four.
Hero changes are also coming in this PTR update - Junkrat, Orisa, Roadhog, and Widowmaker the ones to receive them. To read the full PTR patch notes check it out on the PlayOverwatch website.