Grape wood would probably be best.
Other than that, any hard wood that doesn't have a sticky sap or resin. If you use natural wood that you've collected, it *must* be properly dried and disinfected first. It should be baked in a wood kiln or a conventional oven for several hours to kill any molds, bacteria, or parasites as well as to dry it out.
My iguana uses a combination of grape wood and sumba vine
Sumba Vine