I would love to attend a "lifestyle" party with at least another couple we know and just lose myself in the moment.
I would also love to be in a menage a trois with my wife and any one of her gf - and have an opportunity to just sit back, relax and watch them pleasure each other for a while and then explore the many possibilities of three way sex -

I would also like to make love to a person of another generation - like one of the women here at the office who is a bit older, but I think would be a wonderful sex partner!

I'm sure there are more, so perhaps I'll post later!