Chin Ho finally marrying Malia in "Alaheo Pauʻole". A Wedding Day is heartwarming anyway, but when you consider what Chin has been through and the reasons why he ended his first engagement to Malia, it's pretty clear that Chin has earned his happy ending.
The ending of "Kahu". Can be a CMOA too.
Steve shows up in his Navy dress blues in "Hana I Wa 'la" as a character witness for Danny in his custody battle to keep Grace with him in Hawai'i. Even though his touching speech on why Danny is a great father is interrupted by a Mystery of the Week phone call, it's still rather sweet of him. It's even a deciding factor in Danny winning the custody case. The whole ordeal shows how far their friendship has come since season one.
Just about anything with Max and Sabrina:
Their first date is ruined when she gets shot during a bank robbery. So, he makes a vending machine menu for her and they have their date in the hospital while she recovers.