Civilian Aircraft, for long travel it would have to be the Gulfstream G650. It can fly at .85 Mach and has the same Range as a 747-400 , it also has more luxuries than any Lear Jet.
For Civilian Smaller Jumps it would be a King Air 350. Just because of how Pilots claim it is a very easy to fly, it's safety record, and it's Range.
For Military Aircraft (Prop), I would buy either a F4U Corsair, or a P-51D Mustang, or perhaps a Messerschmidt 109.
For Military Jet's, well most are not allowed to be purchased and owned, but if I could, I would own a F-15 C (Very Similar to E Model but a single seater).
I also wouldn't mind owning an F-4 Phantom (New Advanced Version), or an A-4 Sky Hawk, or an F-86 Saber.