When it comes to versatility, I have to concur with LesSnyder's recommendation of the Savage 24 C combo .22lr and 20 guage shotgun. I've shot this gun in .22WMR and 20 guage. Its a single shot, break barrel, so its simple which makes it easy to clean and leaves little to go wrong. Both rounds are readily available and relatively cheap. The .22lr is easy to learn on, compact to store and light to carry, and useful for small game. The 20 guage is good for everything from bird to deer (using rifled slugs), and they're almost as common as 12 guage when it comes to availability of different kinds of rounds. Finally, its a bit heavy, but it breaks down relatively compactly if you want to take it hiking or camping.