Hottest is definitely the "I'm gonna cum".
How the heck do you control yourself?! When I get to the 15 second mark in your vid, it is as if my penis takes total control and I start pistoning and thrusting totally out of control until the ecstasy takes fire and I cum and spurt - I -cannot- control my thrusting at all, it all turns instinctive, kind of. Very impressive that you can kind of keep still when you climax.