The Native American civilizations have shown us how advanced "stone age" can actually be (and likely was in many part of Europe as well) - better than the few lasting traces of stone-age populations in Europe did.
The Central American populations used a quite advanced weapon with remarkable characteristics; a nightmare of a sword.
The Macuahuitl was basically a club with sharp obsidian stones as saw-like blades. A modern chainsaw is loud, but probably not much more frightening than a new Macuahuitl.
Obsidian is not just some stone; it's a volcanic stone that cooled down so quickly that it formed no crystalline structure. The result is that it can be split with excessively, 3 nanometer sharp and smooth edges. That's better than modern scalpels.
The Macuahuitl was basically a heavy, about one metre long scalpel sword - and it was wielded against warriors who had no metal armour. The club itself was already frightening, the sharpness was incredible, but the effect of a sawing motion slashing attack was certainly so brutal that we won't see a realistic Aztec battle in a movie anytime soon.
The obsidian stones lost their sharpness after some blows, of course. This did most likely require some economic and logistical effort because an army needed to be supplied with fresh stones and the means to fix them onto the wooden club (no clue how that was done).