Being cut during sex?

Yesterday, while activities were going on, my boyfriend reached over onto the counter and picked up what I thought was his phone. And I just thought he was going to take a picture or video of him inside of me from behind.

BUT it was actually his pocket knife.

We have done a lot together, and I have been heavily scratched with fingernails before (not by him though) but NEVER had my back cut with a knife.

And I loved it.

And I still have marks all over my back so it's a nice little reminder of him since we'll be going several days without seeing each other.

Does anyone else like being cut during sex? I know it's not just me, I don't hear it talked about very often though.