My friend created this variant, and I've played it a few times, but he's not in this club so I'm sharing it instead.
This game is similar to duck chess: it's normal chess, but each turn you can tell your opponent a move s/he cannot play. On move one, black could tell white not to play d4. This can lead to some sharp gameplay, as a game could go 1. e4 Nc6 2. Qh5 e5 3. Qxf7, at which point white could tell black he is not allowed to play Kxf7, and the game would end.
Like duck chess, I think that this variant should not just be made as a variant but also a game rule. Obviously it wouldn't work with, say, fog of war, but it could be adapted for 4PC as well as other variants such as Atomic and Antichess.
So I am asking for input. Is this a good variant/gamerule? Could it be added? Let me know!