Half-Life 2 (PC, 360, PS3) | "We Don't Go To Ravenholm..."
In a game as superbly made as Half-Life 2, it's almost impossible to pin a single section that proves just how awesome and ground-breaking Valve's masterpiece is. So we won't bother. Instead, we'll focus on the chapter that gave us the most unbridled balls-out pleasure -  the stunning mix of dark horror, hilarious violence and riotous fun with physics that is the zombie-infested wasteland of Ravenholm.

Eerie from the beginning, Ravenholm is an exercise in how atmosphere and subtle design elevates a videogame into the 10/10 zone. The newly-acquired Gravity Gun immediately becomes an extension of your FPS arsenal in a way that's so natural you can't imagine being without it. And yet, Valve doesn't force the Gravity Gun's abilities on you. It just preps the area, and lets you find out for yourself: "Oh, look, that zombie's been eviscerated by a razor sharp saw blade. "ZAP! " Oh, now I'm carrying the sawblade. " ZZZING! " God! I can fire the sawblade!"

Match this exhilarating ad-hoc action with a lunatic co-star (Father Gregori) and his fantastic zombie-killing contraptions, the introduction of the truly terrifying poison headcrabs - which emit a noise sure to send any Half-Life 2 fan into a shaking fit - and a brilliant finale face-off against wall-climbing super-fast zombies, and you've got one of the greatest levels ever made.

Halo (Xbox) | 343 Guilty Spark
It’s hard to believe today, but one of the original Halo’s greatest strengths was its single-player storyline. A brutal, exotic alien army to fight, a supersoldier with a virtual hottie living in his head, an Eden-esque ancient space station that just happens to be a galaxy-killing weapon - it was brilliant.

Then, just when you thought you’d encountered every possible enemy and were prepared for anything, surprise! You hit this level, which introduced not only a new character - the floating, chattering cube-bot known as 343 Guilty Spark - but an entirely new race of enemies. A grotesque blend of elements from the game Half-Life and the movies Aliens and Leviathan, the Flood were savage, mindless, and horrifying, and their constant bum-rushing en masse required totally different strategy to defeat than any of the Covenant forces you’d already fought. It was a great swerve in an already top-notch game.

Killer 7 (GameCube, PS2) | Alter Ego
From start to finish, Killer 7 does things differently to other games. This makes a lot of gamers say they "don't get" Killer 7. Well, watch the movie of the stupidly entertaining Alter Ego level below and tell us what's not to 'get'. There's the brilliant anime-styled intro, the inspired Handsome Men parody of the Power Rangers/Super Sentai shows (Handsome Light Brown FTW!), there's two men in wheelchairs shooting at each other, there's a genius 8-bit credit sequence... The only thing to 'get' is that Killer 7 is awesome kinky otaku love on a disc.