This is admittedly a rare occurrence, but there are a couple instance where I have posted an answer, was beat out by a few seconds by another user who posted essentially the same answer, deleted my answer, and then realized I had something else to add that could still bring value to the question.
My choices now are either to write a new answer or undelete the old one edit it (or just walk away). What I really want to do is just edit the deleted post directly, and then undelete when the edit is finished.
A few other times I'll realize I've mis-read the question and will immediately delete my post. I'd like to edit the deleted post saying something like "Misread the question, nothing to see here" for other users with 10K rep (I think I've seen one or two of these from most of the frequent SO users), but the only way to do that now is to undelete it first. Of course, I could just do things in the right order in the first place, but I don't always remember.