1. Doug Flutie, 42 in 2004
This entire list is full of players who had extremely interesting careers and Doug Flutie is no different. Antonio Gates was an undrafted college basketball player who became one of the greatest ever at his position, Darren Bennett was a rugby player who came over to be an elite punter, Charlie Joiner helped revolutionize the game of football and Johnny Unitas was the bonafide GOAT when he retired.
Doug Flutie had perhaps the greatest college football moment in history with his Hail Mary win with Boston College, then became a mediocre NFL player, went to the Canadian Football League and became one of the best players in CFL history and then returned to the NFL and was named to a Pro Bowl in his first season back!
I know his NFL career was not the best but he should be a Hall of Famer. It is called the Pro Football Hall of Fame, not the NFL Hall of Fame. Flutie, because of his impact in the CFL and return to the NFL, is definitely Hall of Fame worthy.
Regardless, he signed with the Chargers in 2001 at the ripe age of 39. Flutie started 16 games, losing 11 of them, in 2001 at 39 before being reserved to mostly being a backup. He didn't start in 2002, started five games in 2003 and one game in 2004. He ended his career in New England in 2005.
While Flutie technically only played one game at 42 years old he still was an important member of the Chargers as the veteran backup quarterback. Heck, Flutie was part of arguably the greatest quarterback room of all time in 2004 alongside Drew Brees and Philip Rivers.