When I was 16, I loved lay on my back. My girlfriend would straddle my legs and watch me jerk off. She'd pull up her dress and I'd touch the end of my cock against her pantied crotch. She'd undo her blouse and unsnap her bra so I could watch her breasts.
I think it excited her as much as me. Her panties would get so moist. When I was about to cum, I asked her to 'finish me'. She'd stroke my cock until I shot my cum straight up.