10. The Silent Cartographer - Halo: Combat Evolved
The moment when the first Halo truly "clicked", The Silent Cartographer was mind-blowing back in 2001.
Not just for the opening charge along the beachfront, wiping out scores of Grunts and Elite Covenant, but for the sheer visual spectacle of this massive Forerunner structure built into the side of an island, as you advanced one enemy at a time.
Since launch this has become the most replayable part of the first game; its layout encouraging tactical cover options, replete with A.I. soldiers to lend a hand and a couple of Warthogs to tear around in.
When it comes to progression you're essentially checking into a number of terminals on your way to tracking down the Silent Cartographer itself, but the paths you take from A to B to C are deftly controlled by Bungie on the coding side, providing you don't purposefully run the other way.
You'll reclaim the beach from an overridden landing zone, dive into the first internal structure to wipe out Covenant inside. You'll find a helmet recording of a surprise Flood attack wiping out some UNSC soldiers, only to take on a couple of hulking Hunters on the way to the next checkpoint.
Halo is packed full of phenomenal moments, but this is still one of the best, even against what followed.