Came close to doing this in a club when a couple were fucking with her on top in reverse cowgirl so her legs were outside his and her pussy where people could see.
They invited me to join them and he said to lick her as he fucked her, after ten minutes of the stimulation from his cock and my attention to her clit she came and squirted a huge amount over my face and he popped out and into my mouth, so I picked his cock clean of her pussy juices then they called a halt to our fun just when I thought things were going to go further.
Same club but a different night, I was sat watching a couple fuck. She was sat on his lap with her legs on the outside of his, from the noises they were making it was obvious they were both close to orgasming. She sat still and shivered as she came and I watched him cum in her pussy as he came too. His cock came out of her pussy as she twisted and kissed him then sat astride his legs and I seized the opportunity to go down on her freshly fucked cum filled pussy and spent a good 10 minutes cleaning her out and also cleaning his softening cock up. Once done I stood up and kissed her and they both thanked me but I said I should be the one thanking you as that has been on my bucket list for a while and now I'm looking for a repeat.