Coaches, what are some of the most obscure or seemingly minor things you've ever charted when breaking down an opponent (In any phase of the game)?

Definitely interested if something like that ended up yielding great information.

Great response from someone who wanted to remain anonymous because he's got a great read on a specific coach:

Bill Belichick talks about the time in 2004 when preparing for the Ravens, they had a 100% effective run-pass key on Ravens OL Orlando Brown.

They teach it to their players all week, and then an hour before the game they find out Brown is inactive for that game.