Holland: TomMyyY (*)
Denmark: Byrdi (*)
Iceland: Can't remember his name right now but he has a ninja like character using a 2H and crossbow (*). Anyone can say his name?
Norway: Tor (Pole)
Sweden: Polepoop (Pole), Bagge (Archer), Parre (2H)
Finland: Lerva (1H/Shield & 1H/Shield Cav), Tuonela (HA), Mustikki (Archer)
France: Rubicon (2H), Oberyn (Lancer), Royans (1H Cav)
Turkey: Vincent_Ruth (2H)
Poland: Inhumane (Archer)
Italy: Hellfrag (Archer)
Great Britain & Ireland: Omega (Pole), Strudog (Crossbow), Casimir (2H & 2H Cav), BlueberryMuffin (Lancer)
I have probably forgot about half of the players I know of...
The fanboyism for your own clan is quite obvious.
I'll give it a shot for the countries where I can atleast make an educated guess, fanboyism for Byzantium go!
Austria: Schmacko
Belgium: JackieChan
Croatia: Cpt.Georges, barely plays anymore though
Denmark: GTX
England: Chase
Estonia: Cyber
Finland: Kastu, there is also TuckMunck though.
France: Royanss, best horseslasher in the game.
Germany: Paul, barely plays though and I have no clue how he does in battle, Atze perhaps. Although there are lots of other contenders.
Greece: beer
Netherlands: Tommyyy, perhaps Darian
Norway: Gurnisson? Don't know anyone else, if Tor is from Norway or from Denmark, he's my nominee for whichever he lives in.
Poland: LoR or Rantrex, CarpeDiem is also very good.
Russia: KpuBopy4ka
Slovenia: Vibe
Spain: Lalien, if he's even spanish, always under the impression Warpigs was a spanish clan.
Sweden: Phyrex and Lezard barely play, bagge has archer skills and a good dose of melee skills, but there is also Dezibagel, Bjored and Gravoth, fucking Sweden.
Turkey: Cicero or Hearst, from my own experience I'd say Hearst.
Ukraine: DaveUKR
Edit: Due to my own love for melee fighting and duelling I'm afraid I ignored ranged and cav for the most part and mostly focused on duelling skills.