I'd like a nicely rendered US quarter at about 10x scale (20cm in diameter) with a correct collision hull and friction so that it settles quickly on a surface when it lands, and the heads/tails is easily visible from a standing height in an HMD.
When the quarter is clicked (desktop) it should spring into the air with a random rotation applied, so that it will land randomly heads or tails.
When the quarter is far or near-grabbed and released, a random rotation will added on release, so that an HMD user could 'toss' the coin into the air and it would take on the random rotation when released.
The angular velocity should be such that for a typical toss (or desktop click), the coin will make a whole rotation several times, but not so fast that it isn't fun to watch.
Set a price of HFC25 for this, with a simple marketplace picture of 'Coin for flipping'