Naked Anal
Putting a penis, real or fake, into someone's butt without any help from a condom or lube. Usually done by guys who are still figuring out their sexuality.
'I thought it was a surprise party. Turns out it was a surprise butt stuffing.'
'He didn’t even use a finger. Just went in like he owned the place.'
'I asked for a massage. I got a butt full of cock.'