Armor

On Altaïr

Altaïr does have gloves, boots etc. that appear to be made of leather, but it is unknown if he wears any actual metal armour underneath his robes. It is never mentioned, never seen, never upgraded during the game. One argument in defense of the theory that he wears armour is that in combat, Altaïr can take great amounts of damage without dying. This, however, is most likely because of Synchronization. Desmond, in the Animus, is able to take damage. However, the real Altaïr may have been too great a fighter to take any damage. So, when Desmond in the Animus takes damage, he loses Synchronization with the actual events.

This does nothing to make the idea that Altaïr wears armour unlikely, it only explains a very common argument in defense of the idea that he does. He may wear armour. However, if he does, it is most likely lightweight leather or chainmail armour, because platemail is very bulky and cumbersome, making the acrobatic moves Altaïr performs certainly impossible.

On Ezio

Ezio can purchase different types of armor from blacksmiths throughout the game's various cities.  He can purchase chest armor, greaves, spaulders/pauldrons, and gauntlets. Leather armor is the first available armor and provides health bonuses but no resistance bonuses.  Later, he can purchase Helmschmied, a variant of leather with metal inlays, Metal armor, and Missaglias, a stylized metallic armor.  Each armor after leather offers health bonuses and resistance bonuses.  Armor can be damaged though so it's necessary to repair it at blacksmiths regularly.

After finding and placing all 6 seals in the sanctuary, Ezio unlocks Altair's armor.  Altair's armor is black and offers the greatest health bonuses without necessitating repair. 

File:Armourbuy.png

Buying armours in a shop.

On other characters

Assassin's Creed

Armour does appear on other characters in the game, and there are differences in the styles worn by guards in each city. The guards in Damascus can be found in either lamellar, likely leather, or ringmail armour. Guards in Acre can be found in brigantine armour and chain mail, some complete with coifs. Guards in Jerusalem are often found wearing scale or splintmail. Each of these guard types can be found in the Kingdom near their respective cities. The Knights Templar uniformly wear full suits of chain mail covered in a white tabbard with a red steel helm covering their face.

Assassin's Creed II

All types of soldiers in Assassin's Creed II will be armoured: some "regular" soldiers, some "archers", the "Paranoid" Halberdiers, even the fast moving "Agiles" and of course the heavily equipped "Brutes".