One of the best multiplayer maps from Halo 3 has officially made it to Halo 5: Guardians in a semi-official way. The map itself wasn't designed by 343 Industries for Halo 5, but it was designed by a Halo Forge user that based their design off of the original.
RunNOKYARDrun and nillapuddin626 made a pretty spot on remake of Halo 3's Avalanche map, but with their own twist. They did a great job at bringing it life.
"This is Avalanche by runNOKYARDrun and nillapuddin626. It is a remake of the Halo 3 map Avalanche. It’s a pretty accurate remake of the map, everything seems to be sized correctly. The major difference is that the creators added their own aesthetic to the map, a renewed Forerunner style. The weapon and vehicle layout is mostly the same as the original map but some things were moved or replaced. Overall I think that it’s a great remake and you should totally give it a try. If you do play on it then please don’t use BR starts, use pistol starts."
You can download the map here.