Gemini 6A is best known for achieving the first ever rendezvous in space, a key stepping stone in the journey to the Moon. That wasn't the only 'first' it achieved, though.
Gemini 7 was a mission no one was really that keen to fly. The idea of having to spend two weeks crammed into a cabin no bigger than the front seats of a hatchback, unable to stand up or even move around and in extremely close proximity with another person, was really not very appealing. Unfortunately for Frank Borman and Jim Lovell, they were the unlucky duo selected to fly it.
NASA's hopes of landing on the Moon hinged on Gemini 6A's Wally Schirra and Tom Stafford proving that rendezvous with another spacecraft was possible. It took NASA three attempts to launch the astronauts, though, with one coming very close to disaster.