Mannix aired on CBS from September 1967 to April 1975. When I was around seven or eight years old, it was not uncommon to find me outside pretending to be Mannix (when I was not playing Star Trek). This would entail me tucking a cap gun very similar to this one
behind my back, in my pants (just as Mannix did). In addition, I was known to provide my own soundtrack by loudly humming the swingin', killer Lalo Schifrin theme song. I remember this, because I was confronted one time by slightly bigger, older kids in the neighborhood, who just happened to overhear and observe me while in the middle of "playing" Mannix. This caused me profound embarrassment, hence my strong memory of the occurrence.
IMDb plot summary: One of the most violent detective series in TV history, "Mannix" tells the weekly adventures of private eye Joe Mannix, who originally worked for a high-concept computerized firm known as Intertect, but later opened his own agency at 17 Paseo Verde, Los Angeles, California. Peggy Fair was his black secretary, who was frequently kidnapped. Lots of shootings, car chases, fights, and crashes.