"Spirit of St. Louis", a Ryan NYP, the plane used by Charles Lindbergh to make the first nonstop solo transatlantic flight in 1927. It's basically a fuel tank with wings and a periscope to see forward.
X-1, or "Glamorous Glennis", the plane which break the sound barrier in 1947 with Chuck Yeager at the controls. It used a rocket engine, instead of a propellor or turbine.
Ford Trimotor, passenger plane built between 1926 and 1932
Voyager space probe mockup, which visited Jupiter, Saturn, Uranus, and Neptune, and is still sending back data as they approach the Heliopause
Lunar Module mockup, six similar ones landed on the Moon
Lunar Surveyor mockup, several of these landed on the Moon before any manned missions did. Apollo 12 landed close enough to one of them and the astronauts walked over to it and brought some of its instruments back to Earth.
X-24A, the plane used to test the validity of lifting body surfaces and unpowered glide for the space shuttle during 1969 and 1970. The NASA Crew Return Vehicle that was planned was based off of the X-24A design, however it has been cancelled already.
Several early launch vehicles, along with a Tomahawk cruise missile in front
X-29, plane used for testing forward swept wing technology and high maneuverability
Apollo-Soyuz Test Project mockup, an American Apollo and Soviet Soyuz spacecraft docked in orbit for several days in 1975
"Voyager" completed the first nonstop non-refueled flight around the world in 1986
Messerschmitt 262, the first jet engine powered combat aircraft was first flown in 1942, but due to problems with the airplane and supply it did not see combat until the war was almost over, and had little effect on the war.
P-51D "Mustang", probably the best and most famous of the American fighters during WWII. It was originally designed and built for export to Great Britain, but after the US joined the war it needed a long range fighter to escort bombers over Germany. The original Mustang was modified and given a better engine, the Merlin, which turned it into arguably the best fighter of WWII.