Yes, and it's easier to spot than you'd think.
The most common cheat in Rock Paper Scissors is the late reveal. One player watches the other's throw and adjusts their own hand shape in the fraction of a second before their reveal becomes visible. In slow play with no referee, this can be almost undetectable. With a qualified referee watching both hands simultaneously, the timing differential is obvious. The WRPSA's rulebook treats a late reveal as a game violation — the player who threw early wins the point, or the throw is replayed depending on the severity. This is why simultaneous revelation is the foundation of the game's fairness, and why the referee exists.
The second most common cheat is shape ambiguity. A hand positioned between Rock and Scissors — not quite a fist, not quite two extended fingers — is a Schrödinger's throw. In casual play with no referee, the thrower can retroactively claim whichever interpretation won. In sanctioned matches, ambiguous throws are called dead by the referee and replayed. The solution is clean, committed reveals: a fully closed fist for Rock, a completely flat open hand for Paper, or two fully extended fingers for Scissors. Any shape that requires interpretation is a failed throw under official rules.
Adding unofficial gestures — the "dynamite" move (fist with extended index finger), "grenade," "nuke," or any other invention — is common in casual play and explicitly prohibited in competition. These aren't technically cheating in a casual game if everyone agrees to the expanded ruleset beforehand. In a sanctioned match, they're illegal moves and subject to penalty. The official game has three throws. All claims to additional beats — "dynamite beats everything," "nuke beats rock" — are invented rules that don't exist in the WRPSA framework.
Psychological manipulation that crosses into prohibited territory is the gray area. Verbal misdirection — saying "I'm throwing Rock" while planning to throw Paper — is legal in casual play and common competitive practice. What's prohibited is anything that physically interferes with the count: disrupting the opponent's rhythm, making contact during the priming phase, calling the count in a way designed to obscure the reveal moment. These violations are adjudicated by the referee.
In practice, cheating at competitive Rock Paper Scissors is self-defeating in a way it isn't in many sports. The game is short enough, and the rules simple enough, that blatant violations are almost always visible to the people in the room. The reputational cost of being caught cheating at Rock Paper Scissors — a game where the legitimate skill ceiling is already underappreciated — is higher than the competitive value of a single won match. Most competitive players simply play straight. The game is more interesting that way.