I find concession as a concept kind of fascinating. Forfeiting is fine and all, games like Chess treat that as a default state. But games that utilize concession as a core mechanism are particularly interesting. The easy example is Backgammon, the classic double or nothin'. Marvel Snap has been making use of that exact concept with very little alteration to great effect.
One of my favorite recent examples is Jon Perry's Air, Land and Sea, which is all the more appropriate considering Snap is basically a CCG version of that. Each card played makes the round worth more for the winner, but you can concede the turn at any moment to guarantee a smaller loss. Every turn requires you to evaluate the board state but it's never overwhelming . Simple, clean, effective.
The key is to make concession feel satisfying, and as long as the stakes are sufficiently high I'd say that's pretty easy. Where that gets challenging is in games with multiple players, but plenty allow for players to pass for some kind of benefit (Knizia's Taj Mahal comes to mind). That's almost the same thing already. Why not have more rules-supported concession?
