Completed:
Get fucked
Get blown
Eat pussy (more specifically face-sitting)
Anal
Period fucking
One night stand
Cumming inside and still continuing to fuck (it's messy)
Related to nudism:
Sex on a nude beach
Getting my wife to sunbathe spread-eagled
Getting my wife to socialize and hold a conversation with her pussy in full view of other people
Pending:
The only thing I care to still experience is and FFM threesome. Got close with my ex-wife when we met a woman at a nudist get-together who hit on both of us pretty hard (she kept trying to grope us). Her kink was covering body parts in liquid chocolate and licking it off. We respectfully declined to go to her house; we had to get back home. But then she was subsequently kicked out of the group for being too kinky.
Ever since then an FFM threesome has been on the back of my mind. My current wife has done it when she was in her twenties; and says it's a "one and done." So I guess I'll just have to use my hall pass after all...