While pickup lines are typically meant to be lighthearted and flirty, some can take a more melancholic or sad tone. One example of a sad pickup line is:
"Are you a magician? Because whenever I look at you, everyone else disappears."
This pickup line conveys a sense of loneliness or isolation, suggesting that the person delivering the line feels a strong attraction to the other person, but it also implies that they feel disconnected from others around them. It has a bittersweet and poignant undertone that might evoke feelings of sympathy or introspection.