I really liked Denver's Trango Tower proposal:
(denverskyscrapers.com)
(denverskyscrapers.com)
This was part of the Conjuntive Points in L.A./Culver City(see earlier Arts Tower post)
(la.curbed)
It was to go over a garage, and the columns were even built for it, but it is a no-go
Nouvel's Tour Sans Fin, would have been the first European supertall, and a fantastic design for LD:
(eras.free.fr)