Gibbs rule no. 9: Never go anywhere without a knife.
When Jimmy makes a joke about his prestige level on "Call of Duty: Black Ops 2", it can be related to the actor who plays him, Brian Dietzen, as he does in fact play "Call of Duty" along with co-star, Sean Murray. They have made jokes about other "Call of Duty" titles and games such as "Skyrim" throughout the seasons. They also have attended the biggest gaming event yearly called "E3", and interviews can bee seen of them talking about games they enjoyed to watch and play.
Ricky Whittle, who plays Lincoln, is also in the series The 100 (2014), where he also plays a Lincoln.