Looks like you could be opening a can of worms here! With no basic parameters given, it's hard to advise you. We have the inline folks giving their input, but we don't know if you want modern or traditional.
Okay, you did say both smokless and BP so that sounds like inline, and the only one to do that is Savage.
For traditional, the Lyman Great Plains Rifle is hard to beat. It comes in flintlock or percussion, and has a roundball twist rate. As far as critters larger than deer, Alaska has a minimum caliber for big game (except deer) of .54 roundball, or .45 caliber, 250 gr. for conical bullets. If you want to shoot conicals, you really should use a faster twist than 1:66" for good accuracy. Lyman does offer a 1:32" twist drop in barrel for the GPR, or you can go to their Trade Rifle. This has a 1:48" twist which is a good compromise to shoot both round ball and conicals.
If you want to get something fancier, get a copy of Muzzleloader Magazine and check out the ads.
If you don't want to spend a whole bunch of bucks to get started, you might seriously consider the Hawken which Cabela's sells. It is surprisingly accurate and won't break the bank.
Then you need something to cary your powder in. When I started playing with BP in '68 I had a spout which replaced the cap on a can of powder and that worked fine. A cheap powder horn will do, or a powder flask. Then you need a powder measure. There are several available from Thompson Center as well as others. You always want to pour the powder into into the measure, not from the flask into the barrel. If there are any embers left in the barrel the whole thing could explode and ruin your day, big time. If you go with percussion, you need the appropriate caps (primers for the inlines). The flintlocks I have bought new came with a flint to get started, but you will need to get some more. Powder of course to make everything go "boom." And bullets. If you are shooting the round ball, you also will need patches. If the gun doesn't come with one, get a cleaning jag.
Hope this little dissertation helps. Let us know how you make out!
-Kees-