What's the sexiest thing you've ever done for a partner before you ever had sex or even touched each other?

I once had a bedroom with windows out to the rest of the house. When my girlfriend came over, she'd always make me hot and bothered, but we hadn't progressed past the making out stage. One night I asked my girlfriend to stand outside these interior windows of my bedroom. I went in, stripped naked, put a towel out on my bed, opened the curtains and started to jerk off. She watched me, and got really hot! Sometimes she would touch herself, too. I would cum on the towel, wipe myself off, and get dressed, and then we would start making out again. After we started having sex, we both continued to enjoy these little shows -- but she couldn't always stay on the other side of the glass! It is the hottest thing that I've ever done without touching her.