I'm glad you asked! This is something I know about.
The Aztecs had groups of warriors called eagle warriors and jaguar warriors, who dressed in animal costumes, used shields, and fought with maquahuitl, which were like sticks edged with razor-sharp stone blades. According to the Spanish conquistadors who fought against the Aztecs, these weapons were sharp enough to cut off a horse's head.
Aztec eagle and jaguar warriors with maquahuitl:
Spears were also used by the Aztecs. They also had a weaker melee weapon called a macana, which is like a wooden sword. Sharp enough to be dangerous, but not nearly as good as a real sword.
[img]http://www.orinoco.org/dbase_images/0204_big.jpg[/img]
Another Aztec weapon is the atlatl, which is like a big wooden spoon used to throw small javelins with extreme force. These take a little time to load, but drastically increase the amount of leverage with which a javelin or dart can be thrown, so the attack speed should be low but the attack strength and range should both be good. They also used regular slings (not slingshots) which were surprisingly effective against armor. The sling stones could also be set on fire. Bows were also used.
It should be noted that the Aztecs never mastered metalwork. Their weapons were all made of wood, stone, and other non-metallic materials. Also, since the New World had no horses until Europeans came, the Aztecs never had cavalry. Most warriors were very poorly armed and poorly trained, and very little armor was worn. The Aztecs relied on numbers, mobility, and ranged attacks, so most of their units should be cheap and weak. Jaguar and eagle warriors were skilled veterans who were much better equipped and had light armor.
Other things to consider:
Eagles and snakes feature in Aztec mythology.
Aztecs made a lot of human sacrifices involving cutting out the victim's heart.
One of the Aztec gods was represented as a colorful feathered serpent.
[url=http://upload.wikimedia.org/wikipedia/en/9/9f/Quetzalcoatl.jpg]http://upload.wikimedia.org/wikipedia/en/9/9f/Quetzalcoatl.jpg[/url]
They had a kind of farm called a chinampa. See here:
https://secure.wikimedia.org/wikipedia/en/wiki/ChinampaYou can read more here:
https://secure.wikimedia.org/wikipedia/en/wiki/Aztec_warfareUnit suggestions:
Warrior - very cheap unit, no armor, weak attack with a macana (sharpened wooden blade)
Spearman - cheap unit, no armor or light armor, spear attack (range 2?)
Stone Thrower - cheap unit, no armor, medium strength attack with a sling for impact damage
Eagle Warrior - advanced unit, medium range, strong ranged piercing attack with an atlatl, leather armor
Jaguar Warrior - advanced unit, strong melee attack with a maquahuitl, leather armor and shield
Coatl - most powerful unit, feathered serpent
Priest - heals units
Chinampa - farm, produces food
Pyramid - main building, produces slaves
Calmecac - trains elite warriors