Nice thread
I am lucky enough to have pretty long list of flown on includign a few relative rarities like HP herald and IL 62 as well as Conway engined 747s and DC8 the latter with their extending deployable silencers ( !) but would have liked the 747 Sp to complete the Boeing family and a decent big piston-has to be a Starliner but a 1049 connie would be fine.
If I had to choose juat one though it would be a CV 990 -made a great distinctive not loud noise (from the outside at least) - had weird rear fanned turbo fans and super 1960s cool giant 'speed fairings' on the wing trailing edges.
PB