The one mentioned above where they go train-surfing. I love the scene that starts with Dick giving Tim noogies and the two of them playing tag in the Wayne building. Also their fight at the Lazarus Pit that ends in hair kissage (that happens not long before this story; Tim references feeling badly about it and Tim says he's got nothing to be sorry for).
I also love that when Tim breaks the world record for skydiving Alfred and Tim are waiting to pick him up, and Tim has made him a #1 Space Ranger button.