Don't get me started. I can think of a couple that I am willing to share, but I don't know if they are naughty:
1. A couple of years ago, I spent some time learning about BDSM. You may remember a couple of my posts. Well, I began my journey into Urethral Sounds. At the same time, in order to experience a variety of experiences, I was also visiting an un-nameable massage place that no longer exists. During one of my visits, I took along my sounds and I asked my masseuse to insert them. She had never done anything like this before so there was a risk. However, the funny thing was that although she gladly agreed and followed my instructions closely, she herself was so apprehensive that I think she forgot to breathe and ended up almost fainting. After sitting on the floor for a while to recuperate and recover, we decided that it might not be a good idea to continue.
2. As mentioned above, BDSM is a hobby of mine (all aspects: Bondage and Discipline, Domination and Submission and SadoMasochism. I discovered that I am a Switch) and I had visited a Mistress to learn and experience something new. She told me about breath play and I was so intrigued that I asked her to demonstrate on me; which she did. Wow, what a rush. What an experience. You need to trust someone implicitly to allow them or ask them to do this, but when you do you will find it amazing.