I use both wood and carbon.
I say "wood" because I've used cedar, poplar, maple, ash, and hex shafts. I like the maple and ash for the heavy weight, but they are a bear to straighten.
I mostly use Grizzly-Stik carbons. They are a full length taper carbon shaft from Alaska Bowhunting Supply. They are expensive, but tough as nails, and the taper makes them very forgiving of spine.
They work good too.