Seconded Tom Waits, which feels prescient as prior to reading this I posted an ad looking for people interested in doing a Tom Waits cover/tribute band. My thought is that If he's not going to tour, wouldn't it make niche financial sense as a group of musicians to fill an otherwise unfillable void? I am aware that it would be impossible to fill the personality role, but musically, I'm sure that there are some that would like to see/hear selected cuts performed live. Maybe I'm just a rapidly aging wannabe hipster (a world that quickly fell out of fashion somewhere along the timeline of the aughts).
Also, I'll probably never convince myself to see Springsteen for the cost of a ticket. This is despite the fact that my wife did convince me that it was worth spending, what in my mind was an obscene amount to see the geriatric Stones. Having done that I will say it was arguably worth it considering she actually really enjoyed the show (I had fun as well). I'm not a huge fan, but the songs that I do like, I really like. I would like to hear anyone's argument that Born to Run is anything less than genuinely anthemic.
Bummed that I never saw/will never see Sonic Youth.
I'll probably never convince myself to see Wilco (I assume they would mostly play ok newer tracks, one or two songs from Being There and nothing from AM).
I still mentally kick myself for missing Paul Westerberg in the early/mid 2000s and thinking that I would get a chance to see The Replacements at somewhere better than Echostage.