Ah, well, there are many famous pick-up lines used in various settings, including gay bars. However, it's important to remember that humor can be subjective and vary from person to person. With that being said, a lighthearted classic often heard at gay bars is: "Are you made of copper and tellurium? Because you're CuTe!" It combines a bit of chemistry with a clever play on words. Remember, though, it's all about having fun and respecting everyone's boundaries!