A friend of mine works at China Beach, doing non-nuclear weapons design and testing. One of his "specialties" is air firing systems (they allow non-destructive testing of projectiles). It would be fun to see how the marksmen did with a couple of his creations.
This video is of an airgun firing a golfball at a watermelon. The golfball was traveling at about 410 mph:
410 mph golfball meets watermelon
And this is probably the largest potato gun in the world. No pictures of it being fired yet though. He's been too busy with other priority work to get a chance to play with "Vera" yet: