If you had to pick one out of all the games which one is THE ONE.
That mission that you always play the most. The one that encompasses Halo for you.
You could also go with like a pair of consecutive missions with the same theme, like “Delta Halo \ Regret”.
Or just one per game. However you like it.
I’d say for me it’s: “The Silent Cartographer” followed by “Assault on the Control Room”. That combo is just what Halo is all about for me.
And as a very close second it’s “Pillar of Autumn” from Reach. A grand and epic end to a beautiful story. Which interestingly is also the beginning of the actual story in CE.
Two Betrayals. I know many consider it a difficult slog but I find it has strong weapon, enemy, and vehicle variety along with a good atmosphere and a nice mix of close and long-range combat.
I could definitely pass on the numerous duplicated rooms, however.
The Covenant from Halo 3 has always been my absolute favorite mission of all time. That opening cinematic with the humans and elites storming the towers together was iconic. You got to fight the Covenant for the first half, and then transitioned to the Flood for the second half. And as if that wasn’t enough to make this a cool level, you actually got to fight alongside the Flood for a short period. THEN you finally got to see Truth meet his end at the hands of the Arbiter.
Beyond all that, you could drive all manner of vehicles from driving to flying: warthogs, mongooses (mongeese?), scorpions, wraiths (AA wraith if you got the glitch right), hornets, banshees, ghosts, prowlers, choppers… it was one of the most varied levels in terms of terrain as well, with grass, interior corridors, and snow.
And as if that wasn’t enough again, you fought two Scarabs before getting to fight alongside the Flood.
> 2533274841265539;2:
> Two Betrayals. I know many consider it a difficult slog but I find it has strong weapon, enemy, and vehicle variety along with a good atmosphere and a nice mix of close and long-range combat.
> I could definitely pass on the numerous duplicated rooms, however.
I literally just finished Two Betrayals on Heroic difficulty yesterday and can say with great confidence that I do not like that mission at all lol. Maybe if it was shorter it would be fine, but I felt like it just dragged on and on and on. Eventually I just used some speed running tactics during certain key moments.
> 2533274841265539;2:
> Two Betrayals. I know many consider it a difficult slog but I find it has strong weapon, enemy, and vehicle variety along with a good atmosphere and a nice mix of close and long-range combat.
> I could definitely pass on the numerous duplicated rooms, however.
It’s a great mission. I don’t even mind the duplicated rooms.
Getting to see the Flood battle the Covenant was so cool the first time because that stuff doesn’t really happen in games, even today.
The Silent Cartographer is to me the quintessential Halo mission. Awesome beach landing, a sense of mystery, great pacing.
Winter Contingency was an amazing mission. I think it showed off Reach well. Introduced us to the wild life, locals, and Noble team. I think it set the tone pretty well for the game.
Gonna get a lot of flack for this, but The Breaking from Halo 5. People say it’s too repetitive, which to be fair it kind of is, but compared to other slogs like Two Betrayals, The Library, or Cortana I really don’t think it’s that bad. Forerunners are the most interesting part of Halo lore to me, so that part where Cortana and Warden talk to you while you’re riding on one of the elevators to the next section (“For eons the power of the Forerunners…”) while that classic Halo chant plays over the dialogue, then The Trials playing while you’re clearing the room and then that heartbreaking conversation between Chief and Cortana’s shell… I love it so much. I know I’m the only one, but you won’t be able to change my mind.
I still have fond memories of playing AotCR LAN co-op with friends.
> 2535411561717249;7:
> Gonna get a lot of flack for this, but The Breaking from Halo 5.
Sure, if you like it you like it. Why not?
My issue with that mission and any other mission from Halo 5, except Blue Team is the enemies.
For me the Prometheans are just not fun to fight against. I’ve talked and posted at length about this.
My favorite is Midnight from Halo 4.
It’s got two of my favorite tracks from Halo, ‘117’ during the Broadsword run and ‘Arrival’ when you’re fighting your way to the Composer. Both of those pieces make that whole level so epic and emotional.
I also enjoy the Broadsword run. It’s always fun to me to change up the gameplay for a level, like flying the Sabre in Reach.
And it’s really a gorgeous level all the way around Definitely my favorite.
> 2535461885974839;10:
> My favorite is Midnight from Halo 4.
> It’s got two of my favorite tracks from Halo, ‘117’ during the Broadsword run and ‘Arrival’ when you’re fighting your way to the Composer. Both of those pieces make that whole level so epic and emotional.
> I also enjoy the Broadsword run. It’s always fun to me to change up the gameplay for a level, like flying the Sabre in Reach.
> And it’s really a gorgeous level all the way around Definitely my favorite.
Forgot about this one, easily my second favorite. Love it.
> 2535461885974839;10:
> My favorite is Midnight from Halo 4.
> It’s got two of my favorite tracks from Halo, ‘117’ during the Broadsword run and ‘Arrival’ when you’re fighting your way to the Composer. Both of those pieces make that whole level so epic and emotional.
> I also enjoy the Broadsword run. It’s always fun to me to change up the gameplay for a level, like flying the Sabre in Reach.
> And it’s really a gorgeous level all the way around Definitely my favorite.
Yes totally!! That is a great mission, the music is so amazing and the setting is gorgeous. The quicktime ending is meh IMO but other that that it is awesome.
> 2603643534586909;8:
> I still have fond memories of playing AotCR LAN co-op with friends.
Same, such a fun mission, so nostalgic.
> 2535411561717249;7:
> Gonna get a lot of flack for this, but The Breaking from Halo 5. People say it’s too repetitive, which to be fair it kind of is, but compared to other slogs like Two Betrayals, The Library, or Cortana I really don’t think it’s that bad. Forerunners are the most interesting part of Halo lore to me, so that part where Cortana and Warden talk to you while you’re riding on one of the elevators to the next section (“For eons the power of the Forerunners…”) while that classic Halo chant plays over the dialogue, then The Trials playing while you’re clearing the room and then that heartbreaking conversation between Chief and Cortana’s shell… I love it so much. I know I’m the only one, but you won’t be able to change my mind.
To each his own I guess. 
Here is your flak:
I don’t like the Breaking, gameplay is nothing special, hate the Cortana narrative in H5, also the level is meh visually, forerunner design looks much better in the previous games.
The Covenant in Halo 3 had freaking everything and it was amazing, so that’s definitely up there. I think Mombasa Streets is also deserving of recognition.
Nightfall in Halo Reach. Because of the soundtrack.
Halo Reach Complete Soundtrack 05 - Nightfall - YouTube (from 18:20)
Outskirts, I enjoy the entire map, but I have like 4 missions.