Never apologize. (Season 7, Episode 12, but referenced previous times without a number attached)

Rule #6

• Permalink: Never apologize.
• Rating: Unrated

Always be specific when you lie. (Season 1, Episode 23)

Rule #7

• Permalink: Always be specific when you lie.
• Rating: Unrated

Never take anything for granted. (Season 3, Episode 10)

Rule #8

• Permalink: Never take anything for granted.
• Rating: Unrated

Never assume. (Season 9, Episode 21)

Rule #8

• Permalink: Never assume.
• Rating: Unrated

Never go anywhere without a knife. (Season 1, Episode 13)

Rule #9

• Permalink: Never go anywhere without a knife.
• Rating: Unrated

Never get personally involved on a case. (Season 7, Episode 21)

Rule #10

• Permalink: Never get personally involved on a case.
• Rating: Unrated

When the job is done, walk away. (Season 6, Episode 24)

Rule #11

• Permalink: When the job is done, walk away.
• Rating: Unrated

Never date a coworker. (Season 1, Episode 15, and referenced on other occasions)

Rule #12

• Permalink: Never date a coworker.
• Rating: Unrated

Never, ever involve a lawyer. (Season 6, Episode 7; Gibbs is said to have other rules involving lawyers, but according to Tony, this is the "umbrella" one)

Rule #13

• Permalink: Never, ever involve a lawyer.
• Rating: Unrated

Bend the line, don't break it. (Season 11, Episode 4)

Rule #14

• Permalink: Bend the line, don't break it.
• Rating: Unrated

Always work as a team. (Season 5, Episode 5)

Rule #15

• Permalink: Always work as a team.
• Rating: Unrated

If someone thinks they have the upper-hand, break it. (Season 8, Episode 24)

Rule #16

• Permalink: If someone thinks they have the upper-hand, break it.
• Rating: Unrated