Once you branch out from Hickory, what you smoke with depends as much on what you are smoking as anything. Then it also matters if you are cooking with wood or just using chunks, chips sawdust etc. for smoke flavor.
For poultry and most pork parts like butts, ribs, etc. the fruitwoods like apple and cherry are popular, along with harder to find mulberry, apricot, peach, etc. Sweet smelling smoke. Hard maple is also used here.
For a lot of smoked sausages like polish or even summer sausages, hickory is still #1, along with oak and pecan. Hickory is the flavor you want and leaves a nice red/pink color on the sausage.
Red meats like beef can handle the stronger smoke flavor of hickory and oak.
Pecan is also in the hickory family, but the smoke is milder. Very popular with guys using wood along in offsets. Nice mild smoke flavor and a lot of btu's.
And no reason you can't mix nearly all of these if you want.....as long as you have the general idea of what and when.
Mesquite is tried a lot of times, but I'd confine it to grilling wood only. Hot fire.....grill over the coals. Too strong to use for smoke flavored anything.
A lot of nut trees work, but some don't. Walnut for example is bad. No softwoods like pine or fir ever. No plywood or manufactured woods ever.
