As our games often go forward fast, that question often comes up. Especially when fighting against enemies that can see in darkness, it can become important. It is often ignored, but it can become an effective combat tactic to get rid of opponent's lights.
Black hand is a recurring theme in Ptolus, which is why I decided to create a model of such. In addition, it can be used to present various spells in D&D 4E as well as 3.x rules, and possibly in other rpg's too. And when trying to find more use for it, a subterranean hand that grabs people from the surface sounds quite mean...
These two cardboard ships, a warship and a merchant ship, have seen frequent use in D&D games, as well as in an earlier Iron Heroes game. While IH was a different and refreshing variation from D&D, I find it currently too cumbersome ruleswise.
Here's a paper model of a chemical container train car I've used as a prop in my Savage Cyberworld -campaign. Print it on two A4/Letter sheets, on cardstock, 120g paper or something else strudier than standard paper. I haven't added instructions as the model is quite simple, and I didn't see it necessary to add the parts that attach train cars to each other (whatever they are called in English), model worked quite well without them.
My earlier victory area flags have been quite popular, and because of a request, I've made a new set of flags. I haven't been able to print them myself, so the photo below is from dano903 at http://www.axisandalliesunderground.com and http://community.wizards.com . If you're interested in these flags prepared and based, ask him!