I was obsessed with rubber band guns as a kid. I made a million of them, and I'm sorry to say the cat pretty much booked when she saw me carrying one -- though before you call me cruel, you should know she was much faster than me and I almost never hit her. My favorite gun was about 2' long and was a 2-shot jobber, using the larger sized bands reserved for Sunday newspapers and other big packages -- durable and big. Aw yeah.
I want to continue my unholy fascination with rubber band guns. For inspiration, here's a video of a LEGO rubber band cannon: