For me, chatting to two little kids in the shop who were going out for the day with their grandparents. As I was about to pull out of my parking space, I looked round and they were standing at the next car watching me and the older one gave me the loveliest smile and big wave, copied by her little brother.
Took my DS18 to pick something up and had opened the passenger window to shout on him at one point. As he came back to the car to get in, he came straight in the window head first, all arms and legs, in the middle of a busy street. Made me laugh so much.
Seeing the biggest and fluffiest dog, wearing its Christmas collar, hanging out the car window at the traffic lights. Dogs taking in the view from their car windows is one of my favourite things to see in life 
Anyone else?