Set during leap of faith in the psychiatrists office.
He grabbs Tim's butt and holds on to it. It might be the only thing they have as coming out of their closet as a couple. As far as their professional life goes that is. As couple they are pretty familiar with the Sterling gay clubbing scene. There was just no way they were going to gay clubs in DC, the risk of being discovered was to high.
Tim told him hundreds of times that he would like to tell the team about their relationship, but Tony never went on board with that. His loved for Tim meant more to him than his entire movie collection, but he wasn't ready. He never said it but it was pretty obvious that Tony was afraid that he was going to be send as agent afloat again, or Tim back to cyber crimes, and as much as they loved each other, they loved working for Gibbs more. In the end they still would have each other, if they came out of the closet or not.
But Tony wanted to give Tim something, sometimes it hurted not to give in to the urge to tell everyone about how he loved Tim. So he gave Tim this, a confession of their love. The fact that they were very 'special' agents. Tim played it off as a joke, and that was fine, because he knew that Tim would reward him in the bedroom tonight.