Another video: the Madmen rickroll
A Breaking Bad video: The transformation of WW. (ETA - has many of my favourite Walt+Jesse moments, including Jesse handcuffed to the meth equipment. Here's a follow-up video from the same guy. As he calls himself 'Walter Pinkman' I think he may like the Walt/Jesse relationship as much as I do.)
And here's a speculation about the final scene of Breaking Bad (obviously a big spoiler). It's a comment from the AV Club discussion of the episode. It had never occurred to me, but it could be true. It's also super-super obsessively nerdy about the detail of the Breaking Bad universe.
Gale didn't give the book to Walt. That's my guess anyway. We never actually saw Gale giving him the book. That's the impression they wanted to leave, but I think it was an intentionally misleading impression.
Gale and Walt talked about Leaves of Grass, and then we see Walt reading it. But we don't see Gale giving it to Walt. I think Walt had it already. If you noticed, it looked like a pretty old book; not something Gale would have bought recently and given to Walt (and he certainly wouldn't give Walt his only copy).
Who gave it to him, then? Gretchen. I had to google it, but Gretchen's maiden name was Black. Therefore also G.B.
And the inscription makes sense. And when Walt chuckles when he reads it, he's not chuckling while thinking of Gale; it's a rueful chuckle when he thinks about how he used to work with Gretchen at Gray Matter.
This also explains why Walt wouldn't destroy this book as he did the other evidence of his crimes; Gretchen gave it to him, he knows that, and doesn't think twice about it.
And so the big irony; Hank figures out who Walt is via a clue that shouldn't even have been a clue to begin with.
Remarkable theory. Could be true. Gretchen's name being Black was flagged up several times - they called their company 'Gray Matter' because it was established by White and Black.
Personally I think Gale would have given Walter his long-owned much-loved copy of Leaves of Grass, and inscribed it. And the coincidence of Walt's two business partners both having the initials GB is one of those non-natural things that Breaking Bad features.