Alan Shepard

On Cinco de Mayo, 1961, three weeks after the Soviet Union launched the first manned spaceflight in human history, Alan Shepard became the first American to venture beyond the edge of Earth's atmosphere. Shepard was a Navy test pilot at the time, would go on to serve as chief of the astronaut office during the Gemini and Apollo programs, and to this day is the only person to practice his golf swing on the Moon. You can read more about him here:
Alan Shepard

Shepard is legendary mainly for drawing assignment of the big first all the Mercury astronauts pined for, although Gagarin's April flight muted the sweetness of the milestone. Though no one west of the Iron Curtain had traveled above the somewhat arbitrarily-defined edge of space before Shepard's first flight, Gagarin completed a full 90-minute orbit of Earth while the first Mercury astronauts took on suborbital missions that spent less than 15 minutes at a time off Earth, and never came close to achieving orbital speed. Shepard wanted more, but would spend most of the 1960s sidelined from the space race when Meniere's disease destroyed his sense of balance and left him prone to attacks of vertigo. Since vertigo is close to the top of the list of things that are unacceptable during spaceflight, Shepard was grounded and vented his frustration upon devoted his energy to managing the astronaut office until a cure could be found.

As luck would have it, Shepard's case of Meniere's was treatable by a surgical technique developed around the same time as the Gemini program, and after undergoing successful surgery he was once again cleared for flight status. Initially he demanded command of the first available unassigned flight, which happened to be Apollo 13, but NASA headquarters refused it, rightfully stating that he was too inexperienced to train for the flight in time. Shepard proceeded to assign himself to Apollo 14 with two rookies, allowing him to be the most veteran member of the flight without having orbited Earth a single time, and Shepard, Roosa, and Mitchell left for the Moon as the least experienced crew during the Apollo program. Despite a series of bizarre failures in the command module's docking probe and the lunar module's onboard computer and radar altimeter that three times came very close to ending the mission in failure, the crew of Apollo 14 redeemed the program after the near-disaster of Apollo 13. On top of that, Shepard managed to hit a few golf balls around on the Frau Mauro highlands. Not a bad legacy: