I posted a similar thread on another board, but my favorite scene in a porno are cowgirl scenes where even though the gal is on top, her male partner does most of the "work", holding on to and spreading her ass cheeks wide while vigorously thrusting in and out of her pussy. In the meantime, she's not doing anything except looking back at / talking to the camera and making the required noises while sitting / laying stationary on his cock.
Some of the best examples I can think of:
1. Alexis Texas in Who's Your Daddy 11.
2. Simone Peach In Ass Cleavage 5.
3. Kayla Marie in Internal Combustion 3.
4. Behind-The-Scenes footage of hardcore photoshoots from Pierre Woodman's Castings series.
5. Some older Private films.
Sadly, I haven't found many scenes like that recently, unless it happens to be a slightly older release. :(. Not much CGGDW out there lately. I don't know if it's because the girls are more agressive now or the guys are just lazy.
Let's see more female ass-spreading, active male CG footage dammit!