These Hickey Tats by The Cheeky are both gross and hilarious. And clever! As they say, "Generic hickey's are often meaningless and can be mistaken for bruises. Eliminate the risk of distasteful bruising with a personalized hickytat on your loved one's neck or other body part. Simply place over the chosen region and suck through the perforations."
The seriously crafty could probably D.I.Y. their own version of these for even more customization.