I wasn't entirely closed off to the idea, but I certainly was not seeking it out, nor did I expect to participate in said activities, thinking they were 'kink fringe', if you will.
So, imagine my surprise when during a session that I was completely, inescapably bound to a spanking horse, Mistress' hands found their way to my face. It being completely new to me, I didn't realize what was happening until she did it: her fingers pinched my nose shut with one hand and covered my mouth with the other.
It was really a most interesting sensation. No feeling of fear or panic at all. She is extremely capable and experienced, so I trust her implicitly. Just a few moments of quiet, her holding my head like that, while I thought, Huh... this is interesting. She let go to reposition/get a better grip, and I was able to draw a deep breath in anticipation, then she closed off my airways again for a few moments. It was actually more peaceful than anything; I simply relaxed and basked in the feeling of fondness and trust toward her.
One other time that was exceedingly memorable, well, she had surprised me by having me lie on my back with my legs apart, and bound me that way. I was expecting to have the insides of my thighs beaten, but she instead took out her Magic Wand and spent the next eternity (oh man, it was so good and it felt like it lasted forever!) torturing me with it. After she had been at it a while, she'd driven me to an extreme state of arousal, I was incredibly stimulated everywhere, and close to orgasm. My cloth blindfold was pulled down to my neck; she continued to torture me with the Magic Wand in one hand, while reaching to twist and tighten the cloth around my neck with the other. This mostly restricted my airway, causing my moans and groans to be kind of strangled, struggling to draw a breath. Holy fuck, that was so hot.
It hasn't happened much, maybe two or three times so far, but I have to say that I really like it. Talk about handing over total control to someone! And the trust involved? Fucking hot.