1. Potty-training. I love love LOVE the fact that he will pee and poop on command. Makes my life so much easier.
2. Dog Socialization. Leo has always loved playing with other dogs, but he was a super rude son of a gun when I first got him; ignoring calming signals/body checking dogs who were chasing a ball/not leaving dogs alone. Part of it was just age and him maturing out of it, but I also did a lot to consciously teach him to not be rude. I continued taking him to dog parks but monitored him very closely and would put him on a time out on first offense. He is now incredibly good about playing with all kinds of other dogs, listens to subtle cues, doesn't pester and does not chase dogs who are chasing a ball.
3. Toy Drive. Leo has always loved food, and he did like to play, but I really worked on getting him amped for toys. When I first got him, he was kinda meh about chasing balls and didn't tug at all. He would stop playing Frisbee to eat grass alllllll the time.
Now, he has great drive. When I have a toy, he totally focuses on me and I can train new tricks to him with a toy just as easy and sometimes easier than with food. On the other hand, he is not obsessive at all.
4. "Take a break" "Game Over"
This one relates to the toy drive, but from the beginning I would commentate with "take a break" when we were stopping for a short time and "game over" when we were done playing. This has created a dog who has a high drive and loves to play, but WILL NOT PESTER when I don't want to play. Such a nice thing, and definitely something I will do with all of my future dogs.