Spam subjects I have enjoyed:

Subject: wiener wiener chicken digger Subject: Surprise her with the nicest bag in town Subject: experience queen-sized dick She likes her kitty stretched and do you have the capability to do it?

Some fake spam headlines are good too:

Subject: Clinton found hanged in bedroom Subject: Afghan bombing kills President Bush Subject: Angelina Jolie dies in miscarriage Subject: Michael Jackson gives up being pedophile