I have used public toilets and communal urinals many times, but I have a feeling that isn't what you are looking for.
I remember back when I was much younger my female cousin and I would go into the toilet and watch eachother pee. We also explored our genitals at other times. Never got further than just touching though.
More recently, I had to pee in my friends mouth, and he had to pee in mine (part of the big bet that we finished a week or two ago). It took us a while but we finally managed to pee. Both of us got a bit of stagefright.