The following are some unique NPCs in Cyrodiil.
Porkchop the BoarEdit
Porkchop the Boar is a valiant pig you're allied with in an Arena match in the Imperial City. His fighting skills are unparalleled by any other Boar in the game, and while his nobility knows no bounds, at higher levels he at best assists by tying up a combatant for a few moments, giving you time to deal with other problems.
M'aiq the LiarEdit
M'aiq the Liar is a Khajiit found wandering between Leyawiin and Anvil. He has an erratic schedule, always moves at a full run, and has tremendous speed, making him extremely difficult, if not impossible to find other than through pure chance.
Once found in Vvardenfell (the main island in Morrowind), he has apparently moved to Cyrodiil, and seems to have a better grip on truth. He doesn't lie so much on topics rather than just offer his opinion on them. Every so often goes on five hour hunts for calipers. He primarily complains about certain anticipated features that were not included in Oblivion--fishing, werewolves, companions, levitation, etc. (He does not complain about their absence, he complains about the features themselves--as in, "Why would anyone want to levitate?") Thus, he is mostly an easter egg.
Morag Tong AssassinEdit
The Morag Tong Assassin is included in the Mehrunes' Razor official plugin, in a Jail cell. If you choose to free him, he will wander Cyrodiil and fight, etc. It seems that he has a bounty, and will be hunted by guards. It also seems that he actually acts as an assassin, and has been known to kill Countess Alessia Caro in the woods. He carries a leveled dagger, and leveled enchanted Leather Armor. At level 30+, the Morag Tong gloves grant the wearer Detect Life 100ft, rivaling the Gray Cowl of Nocturnal.
Camonna Tong ThugEdit
If you are the Grand Champion of the Arena, the Adoring Fan will ask to follow you. You can pickpocket him without getting a bounty, but his disposition will lower, which cannot be raised back up. When you kill him, he will respawn in a couple of days.