Whatever your two chosen objects are have all the players write one thing on one side of their whiteboard/paper and one on the other. 

You will then hold up a closed fist with one of the two objects inside, at the same time all players will decide what it is by showing one side of their paper of the other. All those who are incorrect are eliminated and you keep playing until only one remains.

Scoring is, as always, completely arbitrary, you can award only the last one standing, score points per correct guess, or award points on a sliding scale by rounds survived. Decide how you wish based on the number of players.

Objects can be anything but should be small and roughly the same size, more often than not I go with Lego man and AAA battery, but it honestly doesn't matter. 

You can have a third option which is an empty fist, in which case player would hold up neither side of their sheet. But this will result in quicker eliminations and should probably be reserved for larger groups.