Vibrating egg. I've told the story here before, but it's worth a re-run...
When I turned 18 my man and I (yes, the man I'm always talking about here, he's sitting next to me now playing GTA5) went to a sex shop together to celebrate. We picked the remote controlled vibrating egg because it wasn't too expensive or complicated. We didn't even make it back to his apartment.. on the drive home we found a secluded spot to park and fucked in the passenger seat.
I'll NEVER forget... the egg was vibing in my pussy while he was fucking my ass, and he just yelled out, "I can feel it on my dick, I can feel it on my dick! Holy Shit!" as we climaxed together. I wore that little thing out pretty quick, but it sure as fuck was worth the money.