I've played way too many hours of Destiny, and I still hadn't pieced together a lot of the intricacies of both its story and gameplay.
TerraMantis does a good job of highlighting some really fascinating lore and theories on the lore, as well as pointing to some easter eggs and functional secrets. Here's a general rundown of what's in the video:
10. The building that looks like a Spartan head
9. Hive Wizards are female
8. Your Ghost can open (non-mission) doors
7. You can watch your ship get stored in the Tower
6. There's a script on the floor of the Tower
5. A Destiny logo can be found in a footprint in one of the game's trailers
4. Destiny's raid boss, Atheon, could potentially be a good guy (and an atheist)
3. The Warlock's Axiom Seekers can (sort of) be tricked
2. If you headshot the Fallen, you can see their souls escape from their bodies
1. There are quite a few Dark Souls references in the game
Be sure to watch for the full explanations.