1. Nearly every episode of NCIS opens up with a black and white flash-forward showcasing the end of that segment, ever since the fourth episode of season 2 had one.

2. Four actresses have played Gibb's daughter in the flashbacks. Abby Sciuto's discovery of this tidbit in Season 7 led Gibbs and his team to relive this terrible moment in his life. 

3. Gibb's special meetings in the elevator. One of the recurring events on "NCIS" has been Gibbs's unique method of conducting his version of a private meeting.

4. The decade-old "Most Wanted" list. One of the central features of the "NCIS" squad room is the wall of "Most Wanted" pictures.