I have a married friend who is a swinger but with someone elses wife.
Her biggest turn on is to be gang banged and he organises them for her.
He once payed for a hotel room and invited 3 or 4 of his friends from work to gang bang her.
Another time they went to a Paris swinger club and he invited all the black guys there to see to her needs (she is rather classy and her biggest turn on is a muscular, hung black guy or 5!), he told me that he felt a bit inadequate in such company.
He once mentioned doing another of her fantasies which I would have been invited to: she wanted to go into a forest alone wearing only a fur coat then we would have appeared one by one to start the gang bang.
I have proposed my home as his future gang bang facilties so I'll see what happens.