I have.
Before I had become a Witness, I was a born-again Christian. I had a boyfriend in my church who was very tall and his knees bothered him terrible. Often during or after church services there were opportunities ask for prayer, usually with a couple of elders. He asked for prayer that his knee problems would be healed...and they were, right then and there, and he was thrilled, and I never forgot that experience. In fact, if really bothered me when I became a Witness and was told that the miracle had to be from Satan because God didn't do miracles anymore and that he wouldn't have listened to their prayers anyway...I have come to see that the creator is not limited to our understanding or interpretation of him/her.
I have had other situations, such as poulterguise-type demon activity (the kind of blatant stuff that cannot be ignored or written off as imagination....the kind of stuff out of movies) that ended when praying in Jesus name with other believers....and at least one situation where I had a premonition pop into my head that saved my life two seconds later...since my abilities for precognition are not developed, and the thought didn't come from myself, it was as if someone else's thought was spoken into my thoughts, I consider that was also devine intervention, but I don't think that is the "miracle" material you're looking for so I'll leave out the details.