The Ultor Echo mission. The first time you're introduced to the badlands, they make the game feel like an entirely different genre for the mission. The atmosphere for this one is perfect.

My guerrilla fighters were under attack from an EDF guy in a turret on his apc. I managed to sneak around the side of a building unseen, and then charged up to the apc, jumped in the air, and took the gunner out with a sledgehammer to the face.

A "defend the location" mission set in an apartment complex in the Eos area... came into the mission with hardly any ammo from the last run, luckily there was an ammo crate in one of the buildings. Run up to the third floor, reload - snipe at the enemy from the windows. Another enemy wave comes in, and I can't get a bead on them from my vantage. I break out a window on the other side of the building with my gun's melee attack, and shoot out a window one building over. I make the leap, and use the new building to put the enemy in my sights, including shooting the stabilizer off of a flying craft and watching it crash into one of the enemy's propaganda billboards.

This is not even mentioning the joy of rigging things to blow up with explosives, or demolishing an enemy bridge/guard tower/barracks via M.O.A.B. car bomb.

A "rescue the hostage mission" that I solved by slamming through the middle of the building in an apc. I shot a few enemies, chucked remote charges all around and freed the hostages. Back in the apc, with one of the former hostages manning the turret, I ram my way out through one of the far walls. Once I'm clear, I trigger the charges and bring the whole building down behind me. (Unfortunately for the enemy units who were still on the second and third floors)

All of this, plus ethics considerations? I'm going along having a nice time leveling enemy fortifications when low and behold my fellow faction members decide we need to up the ante and start attack a population center! I literally stopped the vehicle I was driving and thought about that.