Mine would have to be Battle Creek from Halo: Combat Evolved!
Hard to say. I will probably have to go with Blood Gulch from Halo 1. It’s just so classic and still fun to play in. I also really like Valhalla from Halo 3.
Canvas - Forge World
Multiplayer - Valhalla (H3)
Camapaign - The Library (CE)
These are my favorite maps.
Valhalla from halo 3. Halo 4’s ragnarok was also really good
Zanzibar, I miss 1 sided objective games.
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Valhalla and Escape From A.R.C.
The pit (h3), lockout (h2,h2a), guardian, haven, mercy, and every midship remake. They are all on the same level to me (:
- Blood Gulch/Cogulation/Valhalla/Rangnarok - Sidewinder/Avalanche - Zanzibar/Last Resort - Midship/Truth - Haven/Mercy - Lockout - Guardian - Sandtrap
Definitely hard to choose, so many great maps over the years.
Valhalla/Ragnarok was definitely my favourite BTB map, hands down.
For normal Slayer/Objective maps, probably The Pit. I had so many epic matches played there, just a fantastic map that allowed so much variety in gameplay, from the mix of long, mid and close range combat, to the larger than average selection of weapons and power-ups.
Cross-map sniper duels, intense battles for the rocket launcher, invisibly stalking enemies while armed with a shotgun or plasma sword, or just straight up BR v BR gunfights.
In my opinion, there isn’t much more you could want from a single map.
Blood and Congulation.
Rather than thinking through every great map throughout the series and making an incredibly difficult decision for myself, I’ll just go with my gut-reaction, the very first map that popped into mind:
Guardian (Halo 3)
Sandtrap! Best map ever. Of all time.
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> For normal Slayer/Objective maps, probably The Pit. I had so many epic matches played there,
I had a triple kill with 1 sniper shot on that map. Right at the beginning of a team snipers match I shot down the rocket hallway, bullet went through two heads, bounced off a wall, and hit a dude jumping by their spawn in the head. Most lucky shot ever, would never be able to find that clip though. 
Definitely Chiron-TL34. Loved that map. I tried to memorize the teleporters and would know my way around the map. Was sad to see it not be in MCC matchmaking at all
Close runner-ups have to be Hang 'Em High, Prisoner, and Highlands (Reach DLC map)
Lockout
Haven
Ragnarok
Zealot
most of maps in Reach.
The original Blood Gulch map. I have had so much fun on it with friends over the years.
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> The original Blood Gulch map. I have had so much fun on it with friends over the years.
Warthog with 1km/h will kill you
Sandbox
Countdown from Halo Reach.Just waiting for 343 to add it.