In my own opinion I thought the Halo 4 end battle with the Didact was pretty badass. They took a minimal approach and I like that. Not like Call of Duty and their 5 minute button mashing combos to beat and strangle a single person (which I think is still pretty cool. MW2's and 3's endings were the best. Though escaping from the underwater facility in Black Ops, and catching Menendez in Black Ops 2 was still pretty cool. The music playing during the underwater escape in Black ops was SOOO badass.)
One of the problems I faced in Campaign was how faint the background music was on some levels. I also liked how they played the Original Halo theme when Chief sees the Halo ring, which made me want it back soo much. I'm not dissing the Halo 4 theme, it's just I would have rather-ed the original / updated Halo theme. I also would have liked at least a couple remake songs from previous Halos, but It'll do I guess. The song that plays during the credits is most definitely from Halo 3 though.
Everything about the Multiplayer and Customization to me was grade A. Some of the maps were bland, but others stood out tremendously. I didn't see a problem with Ordnance, it's just that when the whole other team gets Binary Rifles it's extremely hard to even try to do anything. Maybe they can make it where there can only be a set number of the same Power weapon on the map at one time. Like 2 Binary's at once. I really hated how the weapons despawned sooo fast. I can understand since it's Power Weapons galore in Halo 4, but come on at least keep it slower for Loadout weapons!
I can't really think of anything else so I'll just leave it at that.