If you’ve ever wanted to stand in the middle of a giant zombie horde with a chainsaw and just spin in circles until they’re all dead and you’re dizzy, Left 4 Dead 2 is the experience of a lifetime. It’s an incredible rush — even when you’re only doing it through a gamepad and a television screen — and that image perfectly sums up the thrill that courses through you while slaughtering countless undead in this co-op–driven sequel to last year’s multiplayer masterpiece.

Although much has changed in Left 4 Dead 2, the boiled-to-its essence fun of immolating and annihilating Infected with three friends is still the core of the awesomeness here. Picking up shortly after the first game ended, L4D2 follows four new survivors through the South as they seek rescue from the U.S. military in the midst of a catastrophic spread of the infection that’s turned most of the populace into flesh-hungry zombies. It packs in five campaigns that are each bigger and arguably better than those in the first game, and the settings are as unique as they are crammed with zombies.

“Dead Center” walks you from the top of an infested hotel, down through the inferno-ravaged floors, out through the atrium, and into the streets, where you’ll encounter a gun shop and L4D2’s first curveball: an RPG-like quest. The storekeeper’s locked himself inside his shop, and although he’ll grant you access to his massive weapons cache, he won’t let you pass through his property (blocked by a tanker truck) until you go to the nearby market and retrieve a six-pack of bottled cola for him. The team member who totes the tasty beverages can’t fight, naturally, so the other three will have to protect him. It’s an unexpected wrinkle in a simple formula that only serves to put an even greater emphasis on teamwork.

The finale leads your crew through a mall, where a giveaway-car display is your means of escape. To fire it up, you’ll need to collect a baker’s dozen of gas canisters scattered around the multilevel shopping complex — it’s a not-so-subtle introduction to L4D2’s signature new multiplayer mode, Scavenge, in which the Survivors fight to collect gas cans to power a generator while the Infected try to stop them — all while fending off boss monsters like Hunters, Boomers, Smokers and Tanks. They’re joined by newcomers like the Jockey (who jumps on your head and tries to steer you away from the group and into danger), the Spitter (acid puke), and the Charger (barrels violently toward a target, ground-pounding with his giant arm once he tackles his prey). It’s a tense twist to the series’ established norms.

“Dark Carnival” leads players along a highway and through a motel to the Whispering Oaks fairgrounds, where something about shooting zombie clowns feels like a perfect fit for the series — plus, prizes like Achievements and garden gnomes await (see sidebar below). As you make your way through a variety of the rides (including a slide, merry-go-round, and rollercoaster) to the amusement park’s concert stage, a fake rock show triggers a harrowing last stand in an enclosed arena while you wait for rescue to arrive (not unlike the recent L4D-resembling film Zombieland, actually).

“Swamp Fever,” set amidst the Louisiana bayou’s soggy marshes, is easily the most visually interesting of the group. It’s layered with fog and mostly covered by water, so you’ll move slower and face added challenges here, such as drowning. Yes, because the swamps are often knee-deep or higher, getting knocked down by a Tank, whisked away by a mauling Charger, or jumped by a leaping Hunter leads to death much quicker once you’ve been put on the ground. A mini–final stand in the cabin and on the wings of a crashed jetliner keeps you on your toes (tip: for better odds, set the plane on fire with Molotov cocktails while you fight on the wing), while the actual finale becomes a madhouse as you defend a plantation mansion with the help of a balcony-mounted minigun turret.

The penultimate campaign, “Hard Rain,” rivals its predecessor in atmosphere. The first half is spent routinely enough, moving from a fast-food joint through a sugar mill to a gas station for fuel canisters. The return trip backtracks you through the same areas…in the middle of a series of random, hurricane-like storms that send swarms of zombies at you. A cornfield just outside the gas station is the last place you want to be caught during a downpour as the zero-visibility conditions amidst the corn stalks and rain can get you quickly separated from your teammates. You’ll also need to exercise willpower, for once, rationing out your supplies because whatever you don’t take will be all that’s left on your return trip.

Ironically, the final campaign, “The Parish,” is the most vanilla and L4D1-like of the lot — until the finale. Shooting your way through the streets (and cemetery) of New Orleans, you’ll eventually reach a bridge. Radioing in, the military tells you to get to the other side within 10 minutes; they’re going to bomb the holy hell out of the structure. The ensuing escape is an adrenaline-charged “go, go, go!” sprint across tilted roads and the tops of semi-truck trailers as you try to balance the horde and not leaving anyone behind — stragglers (and backtrackers) are almost certain to die. The thrill of completing it is entirely palpable.

Over the course of your new adventures, it’s the item management that permanently alters how this series plays — for the better. Melee weapons change everything. Baseball bats are all-around effective, katanas are lethal, police batons are undesirable, and chainsaws — with limited fuel — are equalizing ass-kickers. These ammo-less death-dealers are L4D2’s greatest strength, changing the dynamic of the game so that (particularly with the tree-chopping chainsaw!) you’ll actually welcome a surrounding zombie horde, instead of fear it. Even a less-effective handheld like the frying pan is still a great choice because of the hilarious “gong” sound it makes when you whack a zombie with it. After all, at the end of the day, this series is all about lighthearted gory fun.

As far as the gameplay goes, the melee weapons and other new items work because you’re forced to make tough choices. Do you want the stopping power of the Magnum pistol, or would you rather have a mob-mashing fireman’s axe? Both occupy the same inventory slot, so you can only pick one. Same for the Molotov/ pipe bomb and the Boomer bile (which is at its best when tossed at Tanks…so you can see them swarmed by their own kind), the large health kit and the buddy-resurrecting defibrillator or explosive/incendiary ammo packs, and the pills versus the speed-boosting adrenaline shot.

Ultimately, the addition of the melee weapons plus the settings, mini-quests, and events within L4D2’s campaigns make them fl at-out more interesting than those found in the original — a sensation that’s only reinforced by the return of Versus (made better thanks to the compelling campaign settings and a fairer scoring system), the addition of Survival mode out of the box, and the debut of the aforementioned Scavenge and Realism. The latter turns off all “glows” and interface callouts during campaigns, requiring players to stick close together, communicate clearly, and connect to their targets with precise headshots.

Yes, Versus campaigns still take too long for our taste, Survival remains an unrewarding battle against the clock, and playing single-player with bots can never replace the human element of sharing in the tension with friends. But Left 4 Dead 2 is an undisputable improvement over its predecessor in every way, and it steals its own crown as best co-op game on the Xbox. It’s chainsaw-twirlingly good.

On Xbox 360

+ Melee weapons kick ass.

+ New campaigns are bigger and better designed.

+ Multiplayer additions complement overall package.

? What's with the garden gnome? Seriously, who'd want to win one at a carnival?

9.5