"Cheers," - I am an astronomer and don't realise that this is not an appropriate signoff
(on an unrelated note my apologies to all my non-astro colleagues for this bizarre way to end an email)
“Best,” — I am signing an e-mail
“Best regards,” — I am signing an e-mail while exhibiting correct posture and wearing a thoughtful, professional expression
“Thanks,” — I have imposed on you and am hoping to get away with it
“Regards,” — I am seething. I am incandescent with rage