James Stanley devised a subtle way to cheat at chess (and presumably similar games) with a custom gadget concealed in his shoe. It's slow and difficult to use, but there's plenty of room for optimization and he has the perfect name for it: sockfish!
The feet are ideal for this sort of thing, because they're the only part of your body that has any sensible degree of dexterity while still being invisible to casual observers.
Stanley's design has been online for a while, but went viral this week amid an ongoing scandal at the highest levels of the game: World champion Magnus Carlsen withdrew from a tournament after world no. 49 Hans Niemann beat him unexpectedly and was subsequently widely accused by other top players of cheating. Niemann admits that he cheated as a young teen playing online, but says he'll play naked to prove his mettle at the board.
I'm not a chess expert by any means (1720 at blitz, before lunch) but from the scuttlebutt it seems that to whatever extent Niemann had an unfair advantage, it was more likely by learning details of Carlsen's game prep than by wearing a "sockfish" or similar device.