Butt Plug on LetMeJizz
Newcomers picture some giant prop, but most scenes run a modest tapered toy seated in the ass while the action happens up front. It stays put through a blowjob or a straight fuck, the base flush against the cheeks, adding pressure without ever being the main event. The appeal is the double fill, one hole plugged while the other gets worked.
385 butt plug videos here, all HD and all free. New ones go up daily, so check back if you don't find your scene first time around.