My favorite... when a scammer tries to act all indignant in order to get their victims to act quickly.
Begin forwarded message:
> From: jim west [email@example.com]
> Subject: Re: What is going on? Why?
> I have sent you couple of emails, why are you not replying my messages when you got my payment? is this how you treat your client?
No, it's how we treat a scammer who sends a counterfeit check.