Theo discovering what Otis Amber and Crow do in their spare time...and because of it, choosing not to name Amber as his answer to the game.
Dr. Deere taking Chris under his wing, and eventually helping him get the treatment he needs to become healthy and a great ornithologist and scientist.
Also, Deere himself opting to forego the lucrative, yet medically-unnecessary field of plastic surgery in favor of neurology, where he can help genuinely-needy patients like Chris.
The note Westing/Sandy leaves in Ford's envelope: "Money owed for Josie-Jo's education: $0."
Related, although only in hindsight: Judge Ford telling Sandy that Samuel Westing not only paid for her education but made sure she got into the best schools, arranged for her first job, and possibly more. She completely dismissed Sandy's suggestion that the only thing Westing did was pay for an education her parents could never afford and she'd earned everything else herself.
Turtle going to meet Eastman/Westing.
"Hi, Sandy. I won!"
Turtle giving her Mickey Mouse alarm clock back to Madame Hoo. Also, her father starting to teach Madame Hoo more English so she'll cease being isolated is a subtler example.
Dr. Wexler breaking Grace out of her snobbishness and reminding her of happier days when she didn't worry about appearances all the time.
Really, Angela and Turtle's entire relationship dynamic. Angela is resentful of their mother micromanaging every aspect of her life while Turtle is resentful of their mother totally ignoring her in favour of Angela, but the two sisters clearly care about and love each other despite some inevitable feelings of jealousy. This eventually results in Angela pointing the bomb she set towards her own face in order to save Turtle from getting hurt, and Turtle willingly taking the blame for the bombings after she figures out Angela is the culprit.