It's you. Not you personally, but the word "you." And the reason it works so well is that we all do take it personally. When someone uses "you" in conversation, you subconsciously perk up in the same way you do when you hear your name.
I'm sure you've been at a crowded party or restaurant in which the room buzzed with a steady drone of conversation. When you hear your name -- even if the speaker is addressing someone across the room who happens to share your name -- it cuts through the clutter as though they shouted at you. That's why effective salespeople and customer service professionals frequently use the names of people with whom they're conversing. "Now, Bill, have you considered an extended warranty?" Our brains are wired to sharpen awareness of our surroundings whenever they detect the sound of our names.