Gibbs' rules are a big part of his character and Rule #9 is "Never go anywhere without a knife" so the kitchen scene was reinforcing that. All his team members carry a knife.
I recall that after the episode in which Gibbs and DiNozzo both had ZT03** knives, the knife forum chatter about the ZTs went way up as did sales of those knives from internet knife dealers so product placement works. Gibbs also wears a lot of Carhartt clothing prominently displaying the labels.
I wonder how many people who purchased a ZT03** after seeing Gibbs carry one actually liked them when they discovered they weigh a half pound.
All-in-all, I'd say NCIS has been a good knife ambassador and has had a positive effect on the perception of the public about carrying knives and using them as tools. :thumbup: