Boeing 314 Flying boat; probably the biggest contributor to the
idea that people could fly anywhere.
Boeing 747. probably the biggest contributor to the idea that
lots of people could fly anywhere.
Boeing 737 probably the biggest contributor to the idea that people could fly
cheaply (almost) anywhere. Completely killed the romance of air travel as a consequence; now we just whinge about security delays.
B-29 We can hit you. The Manhattan Project cost $2bn, the B-29 cost $3bn. The weapon needs to hit the target.
B-52 We can hit you anywhere
KC-135 Anything we fly can now get anywhere and stay airborne there forever.
Mosquito, a novel idea that worked far better than anyone outside DH expected, and that has had designers ever since continually looking for novel ideas. It's the airborne equivalent of trying to design a better mousetrap.
Spitfire/Merlin - Excellence is beautiful.
Whatever you
first flew solo/operationally.
The DHC-2 Beaver - the airborne pick-up truck