I've had more than one experience worthy of that title, but just yesterday I was reminded of this one.
A winter's night spent at a friend's house when the power was out and we were all trapped there. The time spent with said friends proved an excellent adventure. Afterward, my partner and I stayed in their guest bedroom and slept with our clothing at our feet in order to keep it warm for the morning. Instead of drifting off straight away we wound up having a hilarious and intriguing conversation spanning several hours, which literally started with the topic of dog peen and wound up diverting to the merits of various styles of argumentation, philosophy, how ridiculous it is when people attempt to apply critical theories to written works that existed before the theories in question did, language, various personal moralities and so on. It was at once playful and stimulating, and rarely do I ever experience conversations that satisfying anymore. Hell, rarely had I ever at all before meeting him. The whole thing was conducted in the nude with me laying atop him for warmth, and whenever he would shift off on a particularly frustrating tangent I would simply silence him with either kisses or threats of cannibalism. XD He said I was so much fun and I felt the same toward him, and never in my life had I been so content than in moments such as those.