The electric air freshener is one of those devices that seems like it could only have one possible function, but can actually be repurposed in a few different ways. If you're looking for a practical use, you can turn it into a bug killer, but it's also perfect for pranks.
With a super simple mod, you can make what would be more appropriately called a room UN-freshener. Or, you can take a cue from Calvin over on HalloweenForum.com and turn your electric air freshener into a DIY silly string launcher.
Start by removing the cover and the top faceplate so you can see the motor and wires, then take out the circuit board.
Next, solder the ground from the battery to the ground from the motor, then attach the positives to a switch. Now, just put a can of silly string where the fragrance spray goes, replace the covers, and start making your list of targets!
Calvin used a push-button momentary switch for his, but if you wanted to make it more fun, you could easily use a motion sensor instead. Think of all the kids you could scare on Halloween by hiding it on your doorstep!
For more details, plus a video of the silly string launcher in action, check out Calvin's post.