Print out a life-size picture of your smashed face, laminate it, and put it in a jar with food coloring (tutorial HERE in case you're having trouble grasping the concept). Then set it in the fridge or on a counter and wait for the screams. It works best if you haven't been seen or answered your phone for a couple days and your girlfriend/boyfriend really thinks you've gone missing. Then you can jump out of the closet swinging an axe and yell, "SURPRISE, I'M NOT REALLY DEAD!" You will be able to see the disappointment in their eyes.
One more example after the jump.
Thanks to (No Sender), who I was going to track down and identify before realizing that would take time and effort.