Shard by Stephen Tucker and Kaymar Magic
Stephen Tucker is a creative force to be reckoned with, and this strong piece of mentalism using simple and attractive props is a real fooler!
"SHARD" is super easy to do, with no moves or sleight of hand. The effect is crystal clear, and there's no forces or shenanigans - the spectator genuinely has a free choice, and has no idea what is in the box until it is opened.
You can also perform the entire effect blindfolded if you wanted! (Having a second spectator stand behind you and cover your eyes with their hands is a really good presentational idea!)
'SHARD' comes complete with the custom printed business cards, the ring boxes, ring and dice (you supply your own coin), full written instructions with bonus ideas, and online video explanation!