"NCIS" has been delighting TV viewers for over two decades. The show began all the way back in 2003, and though many "NCIS" actors have left the series, the fans don't miss any of them quite as much ...

Mark Harmon's Gibbs is such an iconic NCIS character, and his list of rules cemented him as one of the best. Although Harmon's Gibbs left NCIS in season 19, he remains a vital character to the show.