Since this resurrected thread seems to have diverged to tampers... Pretty much anything with a flat end that doesn't melt or burn, and isn't otherwise toxic will work. When I'm out in the woods, I usually just snap a twig off of the nearest branch and use that.

The late father of a friend of mine had a good system. He would get a round disposable lighter (as opposed to the usual bics with the elliptical cross-section) and tamp with the non-business end of that. He also would walk around with a smouldering pipe in his front pants pocket. Not sure how he did that without burning himself or the pants, but then again, maybe he did