Campaign/Firefight is all the tutorial you need to figure out Halo. Trial by fire in matchmaking.
Add a Big Ben skull that throws a customizable timer (stopwatch or countdown) on screen for the speedrunner community that got fucked over by the last game.
There are so many cool skulls you could add in Halo. So fun to find, and they really add a cool dynamic to how Halo plays.
Campaign (and firefight for that matter) being what teaches you how to play the game is what I have been saying.
I don't think completely optional things like tutorials for the more complicated things in Halo that one might not know (like, I had no idea how to crouch jump...I still might not exactly).
However, Campaign is where this should happen. Again, like the Rayman example, it ought to teach you how to play the game. Good games do that.
Halo CE taught you how to quickly adjust how you fight and control space by introducing two enemies that fought very differently from one another -- flood and covenant. It was an excellent design mechanic, imo. For one, suddenly changing to flood and not knowing how to effectively fight them made them so much more scary. Once I started getting used to them, the campaign took a turn where now you have both enemies, and it made for a delicious blend that I don't see in a whole lot of games.
I was talking with a guy about Metro: Last Light. Sort of a spoiler, but the game basically is super linear and coddling near the start, then suddenly drops you, and you have to use what you've learned up to that point to make it through. That really makes me want to play M:LL now, because I want to see if it was done well like CE.
Good games teach you how to play them. Viva Pinata is another game that teaches you how to play it extremely well. My main issue with Halo's teaching you is that certain guns and tactics you never learn. Again, the AR simply isn't taught, and it ought to be.
Brutes need to be refined, for example. When coming up against a bunch of brutes, all I normally need to do is throw in a grenade and start spraying AR bullets everywhere. Like I said before, if the AR ought to be used with burst fire fashion of firing, doesn't it then seem counter intuitive to let me be able to effectively make it through a Normal and even Heroic campaign just emptying my clip every time I come to an enemy? I think it's actually somewhat harmful, because then when you get into multiplayer, it's not going to work (well, except sometimes it does; just not very well at all).
Why else do you think we have AR rushe/beat downs?
One of the great things about Halo is it's trial and error approach. Learning how to best strategize about how to get through a situation, I think, is one of it's greatest points. I think that using weapons badly should be discouraged. Doing badly should not be encouraged in Campaign, as I believe they are with enemies like Brutes. I was pretty much stuck with using the AR wrong for quite a while because, hey, it was working, so it never occured to me to change my approach.
Campaign should be the tutorial that teaches you to use it's weapons and tactics through very subtle means. Simply provide feedback to the player that encourages him to develope a better playing strategy. Halo often does this better than many other games, but I feel like it could improve on somethings, like the AR example.
Also this:
Same thing has been said about fighting games for years, but when KI introduced the Dojo Mode and detailed fighting game mechanics, fans loved it. Whether you've been playing FPS's for your entire life or just started with Halo 5, something like this could be beneficial. Needed by you and me? No. But could it help with the majority of Halo's fanbase? Absolutely.
Things like power weapon/power-up/vehicle/etc. spawn timers. Advanced techniques like backpack reloading (343 pls), crouch+jump when you hit a slope to gain momentum, the list goes on.
Yeah maybe when it comes down to just pressing the R/L Triggers at things.. Doesn't teach you diddly squat if you want to get better at multiplayer and in fact, could worsen your aiming since AI movement patterns are much different than a player's.
EDIT: megapost.