Preload Halo 5: Guardians, Achievement List Also Official
Pre-loading of Halo 5: Guardians has begun so you can now start the long download if you happen to have pre-ordered Halo 5. 343 Industries also has the entire achievement list out for you to peruse.
Pre-load Halo 5 now so you don't have to wait on October 27th.
Just of course know that you won't actually be able to play the game until 12:01AM EDT on the 27th of October. Also, Microsoft is going to release a patch for Halo 5 just before release that'll have some more content that's supposed to include supplemental multiplayer material, mostly more maps.
Also, they've released the entire list of achievements in game. There are a total of 65 with the possibility of adding 1000 to your gamerscore, with the possibility of them adding more after the game releases. My favorite is the last on the list; "Benchwarmer - Spectate a game". That might not be achievable for everyone. The rest seem to mostly be fairly easy to achieve, such as completing the single player missions and opening a gold REQ pack, not necessarily groundbreaking in the difficulty department.