Google Calendar: Propose a new meeting time
It’s not a new feature anymore but it might not caught everyone’s eye yet since it’s a bit hidden. Each guest can propose a new time when he receives an invitation and the organizer can review and accept time proposals. It makes meeting scheduling more efficient.
There’s an arrow at the bottom (right side) which opens up further possibilities. One of them is ‘Propose a new time’. Doing that allows the guest to send their time proposal along with an optional message.
The organizer can then accept the proposed time with just one click. Read more about it here.