The Vigilantes, 3rd Viper Squadron, is a long-established unit in the Colonial Fleet before the Cylon attack (Miniseries). Given that the squadron's logo adorns a wall in the quarters of Colonel Tigh (a commanding officer long removed from pilot service), it is likely that Tigh served as a member of the Vigilantes long ago as a Viper pilot in the first Cylon War.
Galactica pilot Captain Kara "Starbuck" Thrace is a member of the Vigilantes (Act of Contrition).
Jackson Spencer, former CAG of Galactica, is also a member of the Vigilantes. He and his squadron were completely destroyed by Cylon Raiders during the Cylon attack on the Twelve Colonies. The only known survivors are Thrace, who was in the brig for striking a superior officer, and the crew of the Raptor supporting the squadron, Sharon "Boomer" Valerii and Karl "Helo" Agathon. It is unknown if the Raptor crew was part of the squadron or just assigned to support it (Miniseries).
Tigh's long time friend, William Adama, is a member of Primus.
Notes
The Vigilantes squadron logo is visible in both Colonel Saul Tigh's quarters and a pilot's ready room on Galactica.