The reveal that Batman knew from the very start that one day Booster would go back in time and try and stop the Joker from paralyzed Barbara. He's been waiting for Booster to grow up into that man and now that the day has finally come Batman offers Booster his hand, telling him that he's there if he ever wants to talk and offering him advice on how to hide his true actions (as he realizes Booster's fake hero act is very much like his Playboy Billionaire act)
The tribute to Ted at the Vanishing Point.
The even-more kvell-inducing tending of Ted's grave til the end of time.
When Booster brought Dick Grayson back in time so he could see his younger self celebrating Christmas with his parents.