My wife and I are going as Batman villains for this coming Halloween. She is Harley Quinn, and I'll be Cesar Romero style Joker. Here is the pop gun prop she is working on . It's a Lone Ranger style cap gun from Goodwill, cost $1 with the barrel and part of the cylinder sawed off and a marshmallow fluff plastic jar hot glued in place of the removed barrel and cylinder. A bit of work to go but she is doing an awesome job so far!