Each ancient Aztec weapon was unique, used for a specific purpose - Aztec warfare was a highly organized, complex affair, steeped in ritual and tradition. We know quite a bit about some of the weapons that were used by the Aztecs, though it appears much of the history has been lost. Manuel Aguilar-Moreno writes:
One finds a repetition of the most important weapons in historical sources, while other weapons receive minimal mention in only a few scattered documents. This suggests that other, less commonly known arms may be forgotten.
So we'll look at the ones that we do know a little about, and briefly discuss each ancient Aztec weapon.
Perhaps the best known ancient Aztec weapon is the maquahuitl (macahuitl). This is sometimes compared to the sword, and it was a powerful, close contact weapon. Like the European sword, they came in two varieties - one handed and two handed. Made from wood (usually oak), they were about 3-4" wide and 3-4' long. The two handed versions might be slightly wider and as tall as a person. Embedded in the edges was obsidian (volcanic stone) or flint.
The maquahuitls were incredibly strong, and the Spanish claimed they could chop the head off a horse with one blow. They were sharp and the Aztecs knew how to use them. They could not thrust like a sword, and so they lent themselves to a different type of warfare.
The picture of a maquahuitl is from The Book of the Sword by Richard Burton. Most likely the maquahuitl usually had simpler grips.
The maquahuitl could be used as a club, but other types of clubs were used. The cuauhololli was a mace made of wood with a ball at the end. It could be used to smash and crush. Various other types of clubs were commonly used, sometimes just made of wood, other times with embedded stone as the maquahuitl.
Another common ancient Aztec weapon was the spear. They were extremely sharp, and sometimes over 7 feet long. They didn't have a small point as many spears you may be familiar with, but a blade a foot wide made of smaller stone blades. Theses spears were known to pierce the Spanish armour, and were sharp enough that the warriors could use them to shave. They are called tepoztopilli. Spears were used in Mexico long before the Aztec empire.
The atlatl was a spear throwing device, for longer distance combat. This ancient aztec weapon is described on The World Atlatl Association website:
An atlatl is essentially a stick with a handle on one end and a hook or socket that engages a light spear or "dart" on the other. The flipping motion of the atlatl propels a light spear much faster and farther than it could be thrown by hand alone.
As you can see, the atlatl was used in other parts of the world and is still used today. The Aztec artists often drew the gods with atlatls in their hands. Darts were used made from oak, single pointed with obsidian, flint, or even copper or bone. The propelled darts tended to be more powerful than arrows.
Atlatls often had a symbolic significance, and some were made with great artistry. One was given to Hernan Cortes by Motecuhzoma II.
Bows, known as tlahuitolli, were common as well. The bows were 5 feet long, and the arrows (yaomime) were pointed with flint, bone or obsidian, and kept in a quiver (mixiquipilli). As with all their weapons, the Aztecs were very skilled in using the bow and arrow. It is believed that the arrows could fly 450 feet or more.
Another devastating ancient Aztec weapon, the sling was made with fibers from the maguey plant (latin agave americana). The slings (tematlatl) were used to send stones flying toward the enemy. They were thrown so powerfully and accurately, that they could do significant damage to a soldier in full metal armour.
The Aztec warrior didn't just pick up stones on the battlefield - they would be prepared ahead of time, carefully shaped. It is believed that the stones could be thrown farther than the arrows could be shot - perhaps over 650 feet.