Despite what you're seeing here, never let your Local Comic Shop Guy (even Mike Sterling) tell you what to buy your wife as an anniversary present. While Beloved wouldn't be totally surprised if I came home with a clock that shot projectiles into the wall on an hourly basis, I don't think she'd be as delighted as June Cleaver there.
Put your money back in your pockets, kids. I checked, and it ain't a real cannon. If someone were to put a cannon under my Christmas tree, I'd be completely stoked! Then I'd teach the neighborhood kids to stay in their own yard!