This is obviously coming from a Dommes experience, but there's something extremely sexy about the "first time experience" with someone. Obviously, you can only get that once with a partner. With a professional, you really don't know exactly what to expect (if you leave your interests open). The anticipation of it, the fear of the unknown, is extremely hot. I feed off that fear/excitement, and it brings out a hunter/primalness that I can't always get with my partner who I've played with over 100x.

For the most part its considered anything that has a medical theme. urethral sounds aka the insertion thru the vagina or penis, play exams, injections, needles, etc.

Scooby
What worked for me was a gradual introduction for my wife. Originally we rented dungeons where my wife would get tutored by the dominatrix...... Once my wife got the latest advice, the dom would leave and my wife and I would have a hell of a time using all the equipment.

As time passed, my wife developed a level of trust in the doms that neither of us anticipated.

On my 60th birthday we rented a dungeon to celebrate (yeah Im old).... after my wife spoke to the dom and the dom "left us alone", my wife blindfolded me and had me on a cross, when I felt her applying clamps to my nipples and all of a sudden I felt another set of hands on my butt and another set grabbing my package.

It was a hell of birthday, but for me was especially fantastic because my wife planned it and participated as well. For me, I wouldn't have it any other way.

Ive been with my wife for 35 years and it wasn't until the 30th year that this took place. So patience worked for me. If your girlfriend is game, you're lucky, but remember.....you can't push a rope.
All the best
The Driver