“No orgasm until...”

Play with denying orgasm as a kinky twist. For example, tell them “You’re not allowed to come until I say so,” or “You can only come after I’ve come twice,” etc. This can be done in a light, playful manner or as part of a Dom/sub dynamic. It builds psychological pressure (they focus on holding back, which can itself be arousing). Ensure there’s no actual health risk – long denial is safe, but blue balls discomfort can happen, so maybe allow some release eventually.