Blizzard have launched a 6v6 Competitive season for Overwatch's Elimination, the respawnless Arena mode where teams simply murder each other. What makes this interesting is that the season is running the Lockout variant of Elimination, where teams are blocked from picking characters they've already used to win a previous round. So sure, you might mash the other team with your strongest lineup in the first round, but what then? With best-of-5 matches, your team might end up with some odd and underpowered lineups - a mode rewarding flexibility.
Blizzard explain that this short season started last night and will end at 1am on May 8th. The usual Elimination maps are in the rotation, and now with Ayutthaya too.
If you want in, look for Competitive Elimination in Overwatch's Arcade.
If you're not the competitive sort, remember that Overwatch has cooperative PvE event modes live right now too. The Overwatch Archives event has added the new Retribution mission, revisiting a historical (in the fiction) Blackwatch operation which ended in gunning through the streets of Venice. Last year's Uprising mission has returned as part of the event too.