Mutual berserk and 1/8+0
This extension allows you to berserk in games on agreement (in tournaments which allow berserk), i.e. you can click "Offer berserk", and if your opponent has the extension and does the same, you will both berserk, otherwise nothing will happen.
Also there are such options as "Berserk back": extension will automatically berserk back each time your opponent does it first; "Berserk always": the berserk button will always be pressed.
Also with this extension you can play 1/8+0 time control (NanoBullet or MegaBullet), if both you and your opponent have it installed (works in ultrabullet games). You need to press "Offer ⅛", and if your opponent does the same, you will both berserk.
You have to be a registered member of Lichess to use this extension. If you want to play 1/8+0, your experience will be better if in your settings you check "Always show tenths of seconds" on this page: https://lichess.org/account/preferences/chess-clock
This extension is new and might have bugs. Report them to my Lichess account "BerserkAsIfUWereMad".