Perhaps this has been covered elsewhere. Perhaps it's of little interest to anyone but that diminishing fraction of us who study words for a living. But the way a comrade signs her emails tells me a lot about the person, likely a lot that I'm just inventing and nothing about her real intent, but still.
First, "cheers." How did this catch on? We're not in a bar. Nor are we in Britain. I just sent you the sales sheet for the spring 2010 publishing season. Is that something to toast? I daresay nay.
Then there's "best." Not best wishes, not best regards. Just "best." This nearly always comes from someone with an MBA or on their way to acquiring one. I need not share further thoughts of mine on that sign-off then.
"Regards." What I like about this, as has recently been pointed out to me, is that in responding to someone who has repeatedly failed or blown off deadlines, your use of the clean, cold "regards" is tantamount to one big eff you. This is truth. Observe in your own irritated exchanges of the future.
All the rest work for me. I stole one from one of my fave folks on the planet, Askold Melnyczuk, who used to sign his letters to me with "all good wishes." I liked it so much, along with the energy it carried, that I just thieved it.
So if nothing else, this serves as notice. I plagiarize. We all do.