A list obviously made by somebody who watches too much History channel.Let's see,
The Bone? You mean people were not using rocks before that, which are both harder and hold an edge better than bone weapons do.
The Phalanx is not a weapon
The Gladius changed nothing, Roman operational methods did though
Longbow, so prior to the English using the Longbow bows were ineffective? Don't tell the Mongols and Parthians that.
Gunpowder - Probably the only thing on the list i would agree with because effective gunpowder weapons changed the paradigm of combat.
Rifled Barrel - not as big a change as you might think. Don't believe me, compare casualty rates per engagement between the Civil War and Napoleonic War and look at the great battlefield killer. Hint, in neither war was it small arms.
Colt Revolver - Do I need to do anything but scoff at this notion?
Belt Fed Machine Gun - I will admit that this weapon temporarily strengthened the defense until doctrine caught up with technology.
Tanks did at least reintroduce mobility to the battlefield although gamechangers they were not.
AK-47 - I laughed out loud when I saw this. So ubiquity makes it a game changer I guess? The weapon is simple to use and fairly rugged but the weapon does not make the soldier; training, discipline, and dedication do that.
Atomic Bomb - did not change the game because everyone is afraid to use them. They are like the guy in a fistfight having a pistol in a holster that he won't use because everybody else will pull their guns out too.
Drones - When they become fully autonomous come talk to me until then I only laugh. They only seem effective because they are used in areas where there is no effective air defense. If they try and use them somewhere with an effective ADA net watch them drop out of the sky like flies.
AK-47, one of the world's most familiar and widely used weapons, creator Mikhail Kalashnikov has “passé l'arme à gauche” (French idiom for kick the bucket)http://www.bbc.co.uk/news/world-europe-25497013
RIP. I think his reactions to the part the ak-47 has played in countless deaths is an interesting one. I imagine that the ak has killed more people in the twentieth century than any other weapon, right?