"I think one of the most underappreciated features of Apple Mail is the “Send Again” command ... Why is this useful, you may ask? Well, it’s a handy way to pass along an email that you’ve already sent without doing a lot of cleanup. I’m sure you’ve noticed that when you forward a message, it by default puts header information in the body of the email and quotes the original text in a different color. When you use “Send Again,” though, it re-creates the message without headers or adding new quote levels. " (from macobserver.com)
I really miss this. If I get the email address wrong I don't want to have to recreate the email again. If I want to send basically the same email again (like a template) I prefer not to do all the copying and pasting again. Send again is really useful and so simple.