Masturbation only is a strong contender no matter what, because you’re guaranteed each time to get what you want and how you want.
Oral. Without hesitation. Preferably 69 x
I could not live without oral. I could live without 69. Never appealed to me much. Love the idea, always disappointed in the reality.
Sex and oral
I’ve mostly gone off solo masturbation since being with my mrs… it’s just not as fun without her! I still get the urge and sort myself out once in awhile however
The number of people who chose solo masturbating surprised me.
edited by mod
It would be the worst, but I think I’m in the same ‘oral’ camp
Terrible situation as I would not want to give up any of these 
but I would have to vote masturbate only as it the one I can control when I do it and there is no way I could give up my toys, especially my wand vibrator.
I’m with @Jocat! I don’t like any of these exclusions.
My first instinct was to say intercourse, but that’s quite selfish for me. Based on our year-to-date stats, of 232 sexual experiences we’ve had together, my wife has had 215 orgasms to my 231. Of her 215, 141 (60%) involved manual stimulation, 51 (9%) used toys, and 34 (14%) cunnilingus. I didn’t track independently what was the cause of each orgasm and they’re not mutually exclusive (oral and toys pair very nicely), but by my best estimate it’s probably about 7% of her orgasms did not involve oral, toys, or masturbation and they were each and every one in cowgirl which she just wouldn’t want to do every day.
Additionally, I would hate to give up going down on my wife as it’s my absolute favorite thing to do. In my fantasies, it’s how we both leave this world together, old and decrepit, maybe in our 90s, she rides my face and just as she has her final, heart-stopping orgasm, I suffocate doing what loved most in this life. Shame for those who have to find us that way. But on the flipside of selecting oral, I’m a really difficult orgasm by oral alone and I just couldn’t do it.
So maybe if they’re not mutually exclusive by partner: my wife can opt to only cum by oral for the rest of her life and I can only cum from intercourse after satisfying her, that might work…
I don’t like any of the options, I can’t answer as one thing can lead to another and another. Plus I couldn’t just stick to one thing.
Oh definitely sex!