FWIW, in chronological order:
Wright 1905 Flyer
The first practical aircraft
Junkers F13
The first all metal, low wing, cantilever aircraft.
Boeing 314 Clipper
The first true intercontinental passenger aircraft.
Boeing B-29
The first nuclear-capable aircraft. Also the first with a pressurized compartment for the flight crew.
MiG-15
Made in more numbers than any jet aircraft in history
Sikorsky S-55
The first successful multi-role helicopter
Cessna 172
The most successful mass produced light aircraft ever built
Learjet 23
The first 'personal jet' aircraft
Boeing 747
The first and most successful wide-bodied jet airliner
General Atomics MQ-1 Predator
The first successful UAV.