I'm not a huge mod guy but Gimli is so prominent in the movies that he deserves a place on my pin (Legolas too but haven't found a place to mount him yet). Gimli doesn't block anything from view except Balrogs side when he's at the closed position. And of course... he's easily reversible.
Materials/tools: Lexan, screwdriver, pen to mark holes, ramp flap screw, bench grinder, scissors.