This dice citadel makes a nifty container for one full set of RPG dice, including space for an extra d10 so you can get your percentiles in there too. The battlements on top unscrew with a quick twist of the wrist.

Update: Some users have reported difficulty slicing the citadel with Simplify3D and slic3r. Give citadel_alt.stl a try if the original citadel file isn't working for you. Also I've cut the into citadel_A and citadel_B for Z-challenged printers.