The Joke virus is just the LoveLetter virus with the subject line changed. There is also a version with "Very funny" as the subject line.

An older virus, but still around (I received it this week) has an attachment called PrettyPark, and a message that says "Test Pretty Park".

Don't open the attachments on any of these. And, as Escamillo said, don't open any attachments unless you know what it is in advance.