I too have loads & loads & loads of favorite parts in all 7 books.
For now though I will mention just one from the 7th Book.
It is from the chapter "The Silver Doe",where Ron returns to save Harry from drowning in that pool & also gets the sword out & then Harry pursuades Ron to stab the locket with the sword.
The absolutely favorite part is where Ron breaks down after stabbing the horcrux 😭& Harry keeps a hand on Ron's shoulder & tells Ron "She is like my sister,I love her like a sister........"(I loved Harry here for saying that😃) & then Ron says he is sorry that he left & Harry says he has sort of made up for it now & Ron says "That makes me sound a whole lot cooler than I am" & Harry says that he is being trying to tell Ron that for years & then they walk forward & hug!
Simply fantastic scene & one of the best scenes between Harry & Ron & the ultimate scene depicting the beautiful friendship they shared! Loved it!😃 While I was reading the book I was feeling totally sad & gloomy about Ron leaving & when I got to this part I felt like jumping up & punching the air yelling "Omg! my Ron is back! my Ron is back!😆