Well personally, my favorite is a small overlooked moment where you see Nick's personlity. I absolutely love the moment in Chasing the Bus after Greg freezes when the bus driver starts coughing up blood. Nick and Greg are walking down the hill talking, and it's here that Nick could have slammed Greg completely. He have said things like, "You don't belong in the field at all" or "You'll never make a good CSI", etc. But instead he tells Greg about green he was in the beginning of his career. The way I see it Nick was the first one, in a small quiet way, to slowly build Greg's confidence about being a CSI. To me, this scene really shows what a great guy Nick is.