A message (call, e-mail, letter,...) from an editor accepting my manuscript. I can't stand all that waiting! I'd prefer an acceptance tomorrow to a rejection today, of course. But if it's a rejection anyway, I'd rather have it today. Why does it take them half a year (and sometimes more than a year) to reject a manuscript?
(By the way, one of the publishers didn't reject my PREVIOUS manuscript yet. The one that I self-published already. If they call now to accept that one, I'd be furious. And I hope I'd have enough self-control to just politely point out that "(1) I self-published that one and (2) there's another one of my manuscripts in your in-box.")