Puzzles involving weight are quite neat in VR. So if you made the skulls and other items like barrels in the caves and dungeons pick-up-able. (Is that a word?) Then you could have pressure pads on the floor, which all need holding down to open a doir. So if your with friends you can stand on them, or if your short of friends, place a barrel on one, or a skull. People like stuff like that. Also ideas with light are cool. Bounce light coming through a hole using mirrors in the room, to touch a particular object to activate a door. These sorts of things have been done before. You could maybe add a twist by making a deathtrap room where you have to solve a puzzle within a certain timeframe or die. A door behind you locks as you go in, and the ceiling starts lowering. The exit door wont open until you complete this puzzle. Get a combination right on a lock. Make a shape using other shapes lying on the ground. It could even be as simple as answering a riddle correctly. Say you go into a room and the door behind locks. A ghost appears and tells you that to unlock the exit you must answer his riddle. Here is a good one. "I never was, am always to be." "Nobody has seen me, nor ever will," "And yet I am the confidence of all" "To live and breathe, on this terestrial ball." "What am i?" Multiple answers come up, and you choose one. You select "Tommorow" and the ghost curses you for solving his riddle and he unlocks the door. Answer anything else, and he kills you.