Daedric. You can get this once you are level 20 or up, or you can use bound speels, repair the armor, drop it, and then you have it forever
Mods.... search halo armour oblivion
you might have killed him by accident at some point that's the only reason i can think of.
Daedric armor provides the best defense out of all armor types, but is a heavy armor. Glass is the best light armor.
The Best Defence in the Imperial City, market section, is guaranteed to have a full set of Steel Armour.
Shadowmere can be equipped with armour, if you have the Horse Armour Pack plugin.
The best armour for an Acrobat would be light armour of some variety. Generally the lighest possible armour would be best, but as you advance in level this would be poorer for combat, by upgrading your Light Armour and Sneak skills though you should be able to get the most advanced Light armour you can acquire though (which will also be the heaviest) and be able to wear that without any penalties to stealth due to the abilities granted by the high Sneak and Light Armour skills.
A full set including shield provides an armour rating of 40 base, modified by your skills.
If your a high enough level (somewhere around 20) you can get them from either the dark brotherhood or off of a creature in oblivion.
You can't mod the console versions of Oblivion. Sauron's Armour is something added by a mod on the PC version.
For the Xbox 360, you can buy the 200 point Horse Armour Add-on.
Sadly, no. :/ but from what ive heard, i think you can create armour and weapons in Skyrim :)
Im not quite sure what your asking, but the guardians of oblivion are the daedra, ( the guys who wield big weapons and run around wearing daedric armour) and most of the creatures in the oblivion gates ie: scamps, clanfear, daedroths, astronachs ect...