As rumours around a new Call of Duty begin to circulate, we run-down the best levels from the most loved and loathed game series in the world.

Info on Call of Duty: Ghosts is set to drop on 1 May, with rumours already circulating that it'll be set in the Modern Warfare universe and star Simon Riley, aka "Ghost" from Modern Warfare 2.

So as the CoD series teeters on the launch of yet another iteration, we've opted to look back at some of the finest moments from the world's best-selling game franchise.

5. "Crucifix Hill" - Call of Duty: Big Red One

A spiritual rip off of Band of Brothers, Big Red One follows the US 1st Infantry through World War II, charting the unit's battles in Kasserine Pass, central Italy and the Netherlands. It's notable for never switching perspectives; unlike earlier and later CoD games, you play as the same character throughout the whole Second World War. It's because of that that Crucifix Hill works so well.

Call of Duty Big Red One
The 1st Infantry fighting in the Dutch countryside in Call of Duty: Big Red One

Since you never swap bodies - since you stay with the same unit - you get to see your friends change over the course of the war. And change they do. Later CoD games feel overwrought and turgid, but there's genuinely quality writing in Big Red One. Crucifix Hill exemplifies that. Set during the real Battle of Crucifix Hill outside Haaren, Germany, it's when you really see how far everyone's slipped. Sgt. Kelly especially, who starts the game a bespectacled, anxious rifleman, is hideous by Crucifix Hill, yelling and killing and covered in dirt. It's a much more nuanced take on the whole horrors of war thing than later CoDs, which can only make the same point with nukes.

4. "Celerium" - Black Ops II

This is one for real old-school shooter fans. After the original Modern Warfare took off in 2007, the CoD franchise generally took place in Middle Eastern urban sprawls and big Russian estates, but Celerium pulls it all back in. In a secret underground base in China, you have to shoot through a series of gun-metal grey corridors and plate glass lobbies. It's knowingly retro stuff, harkening back to the days of DOOM, Timesplitters and Mace Griffin.

Black Ops 2
Arriving at Celerium via wingsuit

It also sets the Black Ops II's big, daft tone, opening with you flying down to the base in a ridiculous "wingsuit" before flipping on an invisibility cloak and targeting baddies with a colourful laser sight. Black Ops II was a great Call of Duty because it dropped all the pretentious "war is hell" nonsense and let the game run with the silly bombast it was always great at. Celerium isn't just a nod to shooters gone by, it sets the bar for a new, much more faithful line of CoD games.

3. "Death From Above" - Call of Duty 4: Modern Warfare

Although Celerium thankfully did away with CoD's high thinking, sometimes the series got it right. Death From Above is a smart, uncomfortable take on US military dominance. You play a TV operator aboard an AC-130 gunship, whose job it is to target Russian soldiers on the ground for airstrikes. Aside from the sickeningly gleeful remarks from your co-pilots ("Oh yeah, good kill, good kill") there's a pervasive sense that what you're doing is just unfair. Dozens of soldiers pour onto the streets below, but before they can take aim and start firing you blow them all up with just a push of a button.

It's dehumanising. The people you're killing are just white shapes 15,000 feet away; instead of having to sweat and move and reload, you just pull levers to execute, kind of like...well...kind of like you're playing a videogame. Death From Above is a really intelligent level. It's not just a jab at the US Military Complex, it also sends up death in games, making you feel uneasy about pressing buttons to kill.

2. "Stalingrad" - Call of Duty

The original Call of Duty set piece, Stalingrad is a carbon copy of the opening scene of Enemy at the Gates, but absolutely excellent nonetheless. You play a Russian infantryman dropped on the banks of the Volga at the height of the Battle of Stalingrad. Though the amount of material stolen from Enemy at the Gates is distracting, this level gives an early glimpse into what would become Call of Duty's signature: Tightly scripted melodramatic set-pieces that aim for pure thrills rather than anything clever.

It's just sensory; it's just wow. It also blows Medal of Honor: Frontline out of the water. Launching in 2003, a year after Dreamworks' educational war shooter, Call of Duty's riff on Enemy at the Gates is similar to Frontline's adaptation of Saving Private Ryan's D-Day scene. But CoD is better than MoH - it beats Frontline at its own game. The Stalingrad level almost feels like a flag in the ground, Infinity Ward's way of proving that its cinematic war games are the best cinematic war games. A decade later, Call of Duty is still on top.

1.  "No Russian" - Call of Duty: Modern Warfare 2

Controversial, and rightly so, No Russian got so far as the House of Commons in 2009 when it sparked MPs Keith Vaz and Tom Watson to form an action group against violent videogames. You play an undercover CIA agent who, in order to maintain his guise among some Russian terrorists, has to shoot dead dozens of unarmed civilians at an international airport. There's no challenge, really, and aside from making the big bad guy seem more big bad guy-y, No Russian serves almost no narrative purpose. On the surface, it's shock for the sake of shock, but it's number one on this list for two reasons.

First is that it's a kind of stronger version of Death From Above. Without any context, or at least, very little pretence, you kill and kill and kill in No Russian with no opposition. Again, it's like videogames themselves: It appropriates killing into something blithe and breezy, and makes that look horrendous. Second is that No Russian kick-started the debate on violent games, not necessarily among MPs but from the gaming media and industry. The sensitivity to violence in BioShock Infinite is an aftershock of No Russian, as are games like Spec Ops: The Line and Hotline Miami. Games now are arguing over violence like never before and No Russian spearheaded that debate.

So, 1 May for more on Call of Duty: Ghosts. Hopefully, when it comes to re-writing this list next year, it'll provide a few new entries.