At the moment I'm pretty obsessed with Harad from the Third Age: TW mod.
Other than that I'll go with Greek City States from Rome, though it's very hard to settle for only one faction.

Medieval Total War 1: Holy Roman Empire, gothic knights up in this bitch.

Medieval II Total War: Holy Roman Empire
Medieval II Total War: Crusades- Templars
Medieval II Total War: Teutonic Crusades- Teutonic Order
Empire Total War: Prussia
Yes I like the black and god look and being the one nation that says fuck you to everyone.

The Kingdom of Hannover. (you know, with that "play every faction in E:TW"-mod...)
Also, if the mod "Third Age: Total War" (LOTR mod for medieval 2) counts, then Harad.

ARMENIA!

That's a hard one...I'd say smaritans or however you spell it from the barbarian expansion

fighting off the vandals the romiltia(FUCK i can't spell today) and he huns is just the most epic battles ever

its like hey all you faggots on the west coast i just saved your asses how about some trade agreements?

The Spaniards from M2TW they were estronk

The Viking faction

And Norway in Britannia Campaign in the Medieval 2 expansion pack

Carthage, Rome total war. i am too lazy to look for a picture

Rome- juilii
medieval 2- denmark
medieval 2 crusades- Templar
medieval 2 americas- apache
medieval 2 Teutonic crusades- Teutonic order
empire- maratha/ prussia
napolean- russia
shogun total war 2- was there any fucking difference in any of the goddamn factions? no 10% bonus on a particular infantry type does not count as a major faction difference.

I'm going to have to say Great Britain from Empire.

Byzantine, first medieval. No other total war games live up to my standards after playing the first one.

THIS LAND IS ROMAN!

(Rome, just in case you didn't get it..)

which faction though?

Poland-Lithuania, Winged Hussars = Rape

Winged hussars is the best hussar

GAUL. RAGGHGHHHHHHHHHHHHH

papal states in medieval 2. Shit was cash

Carthage for the Europa Barbarorum mod

Prussia, Napoleon. Roflstomping France and annexing it all never gets old.

Almohads from Medieval Total War 1, mother fuckers had the BEST generals!

not to whore myself out, but i made a video in Napoleon, anybody want to see it?

CRETIAN ARCHERS IMPERATORRRRR

HELL YEAH, Cretan Archers were my Seal Team Six and SAS combined, I used a half stack of them to back up a half stack of legionary cohorts, they rained death on my enemies.

I tend to enjoy Scotland it M2TW, I don't know why I just kind of play as the mall the time.

Greece, HOPLITES!

NO. Fuck the spartans made online games hell. No matter how many times you cycle charged them they WOULD NOT BREAK. its like their front was a unbreakable phalanx, and then their asses were an even more burly and hardened phalanx.

fucking invincible; pic unrelated.

that's the one where you act like an asshole to people with different hobbies than you