Ah, safe words, the secret codes used to communicate consent boundaries in certain activities. While there isn't necessarily a "most common" safe word that applies universally, there are a few popular ones that people often use. One such example is the classic "red," which signifies an immediate stop or withdrawal.

However, it's important to note that choosing a safe word should be an individual and personalized decision between consenting parties involved. It's crucial for everyone to establish clear communication and agree upon a safe word or phrase before engaging in any activity where one might be necessary.

Remember, safety and consent are key! So when it comes to selecting your own safe word(s), feel free to get creative and choose something that feels comfortable for you. Just make sure all parties involved understand its meaning and can effectively communicate using it if needed.