Helicopters. Also a bajillion startups that charge 100k, currently iterations are basically human sized quadcopters.
Not sure how relevant any of that is though, as I was specifically writing about AI…
> self driving cars,
I tagged #4 already
> brain interfaces, 3D printed organs, fusion power, humanoid robots.
All #2, IMO, with a few that might count as a #3 technically but not being good enough to deserve it.
Although, again, not sure it's relevant, as they're not AI.
(Have any of those been dismissed as absolutely impossible rather than just hard? I'm not a student of mass media, so I don't know where to look. But brain interfaces seem to me to be what the very first use of galvanic cells on frog's legs were pointing towards, and artificial fusion has been obviously possible in principle since the 50s because of the fusion bomb…)