First figure if you want to go flint or percussion.
Predominant among the flint guns are smoothbore muskets, which have their limitations when it comes to accuracy. However, you can always use them as fowlers and shoot nails, rocks and what not - just like the Colonials did at Breed's Hill (better known as Bunker Hill). There's also flintlock rifles out there (military like the US Model 1803 half stock, British Baker, various German Jaegers and non military ones of the Pennsylvannia Long Rifle genre or Southern Poor Boys/Schimmels).
I like the French-Indian War era long rifles. As working guns, they were thicker and heavier (and resultingly stronger) than the gracefully relief carved, ornately engraved, richly inlaid, "Golden Age" long rifle which captures our eye. These were mostly flinters and then the "Decadent Era" of the percussion set in.
Or you can go with the Fur Trade era short, stout rifle for which TC produces their Hawkins and Lyman their Great Plains Rifle. Funny how we started with the short, big bore Jaeger, reduced the bore and lengthened the gun until it became our famed longrifle, and as we moved east, shortened it and opened the bore again (though not quite as much) for a stronger rifle. This era tends to be the most popular one out here in the West Coast (hey, it's only about $250 for the gun).
Don't discount Civil War Muskets either. Those minie ball guns are deadly accurate but unless you cast your own, they can get very expensive to shoot.
