Silly string shooter I designed to be powered by a single servo. Servo mounts vertically on the side where you can use bushings to adjust exactly where the servo horn presses the top nozzle. I've gotten this to work with the cheap MG995 servos, so you don't need anything too beefy. You should be able to print this out of most materials, I've used 98A tpu, but I'm not sure you'd want to use anything softer than that.
The two rectangle holes on the bottom are so you can use zip ties to hold the can in.
Enjoy!!!