Three times that I can think of…
1. Was having a sleep over with my girlfriend, her sister, and her best friend. Having a good time. Lights were out and we had spread out sleeping bags and blankets on the floor. Can’t remember how this all got started but I remember my girlfriend telling her best friend that I was really ticklish. Next thing I knew my girlfriend grabbed my hands, yanked them above my head, and yelled out, “I got his arms, he can’t move, tickle him!” Her best friend straddled me and tickled my underarms and ribs. I completely lost it and laughed and laughed and laughed. The three gals thought it was the funniest thing ever and kept tickling me for the next several minutes.
2. Was getting a massage. The masseuse knew me and knew how ticklish I was. I made a snappy comment and she used this as an excuse to straddle me and tickled me. I laughed hysterically. This probably only lasted for a minute maybe a minute and a half but I remember laughing so hard and was a bit concerned that she wasn’t going to stop. This was the one time I almost panicked while getting tickled as I didn’t know this person that well and didn’t know when she was going to stop.
3. One morning as I was waking up my wife tickled me, which she often does. This time she straddled me and went to town on my upper body. I laughed so hard for the next 4-5 minutes. I was half asleep when my wife got on top of me. For whatever reason, that was the best (worst?) that my wife has ever tickled me.