What are the known memories used to conjure Patronuses?

Question

Inspired by a random YouTube user commenting on this Deathly Hallows clip:

Does anyone know what memory Alberforth thought of in order to create that huge patronus? _AeroRomero

We know that casting a Patronus

"[..] will only work if you are concentrating, with all your mind, on a single, very happy memory." _{Harry Potter and the Prisoner of Azkaban, chapter 12, "The Patronus"}

I only remember one of these memories actually being described, namely Harry's one, which is alternatively thinking about his parents or Ron and Hermione (well, technically that makes for two memories).

As pointed out by Mithrandir in chat, this quote indicates that Snape probably thinks of Lily:

“But this is touching, Severus,” said Dumbledore seriously. ��Have you grown to care for the boy, after all?”
“For him?” shouted Snape. “Expecto Patronum!”
From the tip of his wand burst the silver doe: she landed on the office floor, bounded once across the office, and soared out of the window. Dumbledore watched her fly away, and as her silvery glow faded he turned back to Snape, and his eyes were full of tears.
“After all this time?”
“Always,” said Snape.
_{Harry Potter and the Deathly Hallows, Chapter 33, "The Prince's Tale"}

Some others we can try to guess:

• Umbridge is likely enjoying the Muggleborns' treatment under the dark days of the Second War, with regards the following quote and this answer (as well as other posts on this thread):

  The moment he had passed the place where the Patronus cat patrolled, he felt the change in temperature: It was warm and comfortable here. The Patronus, he was sure, was Umbridge’s, and it glowed brightly because she was so happy here, in her element, upholding the twisted laws she had helped to write.

  _{Harry Potter and the Deathly Hallows, Chapter 13, "The Muggle-Born Registration Committee"}

• Tonks' Patronus took a wolf shape due to her love for Remus, so maybe she was thinking of him, and reversely.

Then there are a couple more which I just don't know: Dumbledore's Army members, Abelforth, Lupin (before he met Tonks), etc.

What do we know from various sources¹ about what memories people thought of to cast their Patronuses? What's the complete list of people whose memories we know and their memories? ²

I'm looking for explicit statements, or at least quite educated guesses, rather than just "Thinking about your loved ones seems to work, so maybe James was thinking of Lily".

---

¹ Let's say that includes Pottermore, books (as well as Fantastic Beasts and the like), video games, movies, JKR interviews, DVD commentary.

² For this question not to be too broad, let us consider the list of Patronus-casters from Pottermore. I'm mainly interested about Order of the Phoenix members, but bonus points for Dumbledore's Army members.

Answer 1

These are the memories that I found explicitly mentioned in the books:

• First time riding a broomstick.

  Harry cast his mind about for a happy memory. Certainly, nothing that had happened to him at the Dursleys’ was going to do. Finally, he settled on the moment when he had first ridden a broomstick.

• Winning the House Championship in Second Year.

  Harry thought hard and decided his feelings when Gryffindor had won the House Championship last year had definitely qualified as very happy.

• Finding out that he was a wizard.

  The moment when he’d first found out he was a wizard, and would be leaving the Dursleys for Hogwarts! If that wasn’t a happy memory, he didn’t know what was. ... Concentrating very hard on how he had felt when he’d realized he’d be leaving Privet Drive, Harry got to his feet and faced the packing case once more.

• Going to live with Sirius.

  I’m going to live with my godfather. I’m leaving the Dursleys.

  He forced himself to think of Black, and only Black, and began to chant: “Expecto Patronum! Expecto Patronum!”

• Celebrating winning the Triwizard Tournament with Ron and Hermione.

  He summoned the happiest thought he could, concentrated with all his might on the thought of getting out of the maze and celebrating with Ron and Hermione, raised his wand, and cried, “Expecto Patronum!”

• Thinking of Ron and Hermione.

  He was never going to see Ron and Hermione again —

  And their faces burst clearly into his mind as he fought for breath —

  “EXPECTO PATRONUM!”

• Imagining Umbridge getting sacked.

  Harry raised his wand, looked directly at Umbridge, and imagined her being sacked.

  “Expecto Patronum!”

• Thinking of Ron and Hermione.

  He raised his wand: He could not, would not, suffer the Dementor’s Kiss, whatever happened afterward. It was of Ron and Hermione that he thought as he whispered, “Expecto Patronum!”

(Interestingly, aside from the lesson with Lupin in which Harry used happy memories, it appears that every other time where it's mentioned he actually uses a happy thought rather than a happy memory.)