I'd love the ability to choose "no signature" easily when composing a new email, from both Desktop and particularly mobile. I already setup an initial signature, with a reduced signature for replies, but sometimes, if I'm emailing a friend or coworker, they don't need to see my main signature at all.
On desktop, I suppose it's easy enough to select and delete the signature, but that's not nearly as simple in the mobile app. A checkbox or simple toggle to turn off the signature would be AMAZING.