Military personnel in uniform are required to salute when they meet and recognize persons entitled (by grade) to a salute except when it is inappropriate or impractical (in public conveyances such as planes and buses, in public places such as inside theaters, or when driving a vehicle).
One notable player, Shawn Kemp, enrolled in college but never played any games due to personal problems. In 1989, a year after his high school graduation, he was drafted by the Seattle SuperSonics. He played 14 seasons in the NBA and was selected to 6 All-Star Games and 3 All-NBA Teams.
Fifteen of those players have never played one game in the NFL, including the first Heisman Trophy winner, Jay Berwanger. Fifteen Heisman winners went undrafted in the NFL, most recently 2003 Heisman winner, Jason White of Oklahoma.