In case it has been a while since you saw someone make their "O" face, that arrangement of the facial muscles particular to the moment they're orgasming, this clip from WatchCut video is here to remind you. And remind you, and remind you, and remind you. It's a supercut of 100 people doing their best impressions of themselves as they come. That's it. That's all. Sometimes, that's enough.
As far as I can tell, they were asked only to show their "O" faces, but they offered up their "O" noises, too, to make sure the viewer isn't missing out—so please, enjoy this minute and 53 seconds of unbridled simulated pleasure.