I have been masturbating since I was about thirteen and it didn't take me very long to learn that I enjoyed stimulating my ass while stroking my cock. I have continued to masturbate on a regular basis.
There was one occasion a few years ago where I was in my basement watching an x-rated video and using one of my homemade dildos on myself. I had it lubed up and was sliding it in and out of my ass with a nice steady rhythm. Pretty soon my cock began to twitch and I began to come without even touching my cock. It was fantastic to be able to make myself come just by fucking myself in the ass with a dildo. That is the only time it has ever happened, however when my wife and I were first married she would sometimes run her finger up and down the crack of my ass and it drove me wild.
I enjoy performing oral sex on her and I would often position myself so that she could stroke and fondle my cock while I gave her hot pussy a long workout with my mouth and tongue. I remember the first time she reached up and put her finger on my asshole and started rubbing back and forth with it that it made me so hot that I shot my load without her even having a hand on my cock. In fact, that has happened a few more times since and I am not even sure she was aware it was happening, but I certainly was. When she is giving me head I will take her hand sometimes and guide it to my ass and push her finger against my anus. Although she has never gone any further than just rubbing up and down my ass I hope someday that she will take the next step and push her finger all the way in and fuck my ass with her finger while I come in her mouth. I often fantasize about her fucking me in the ass with a strap-on dildo while I masturbate. That always get me hot and hard. In fact, I think I will go jack off now.