Formal title of your nation's leader?

[Archonium]

His Imperial Majesty Ceyran Ruvenius Archonis II, The Dragonborn Emperor of Archonium, High King of Arcanea, Andracor, and Phoenixia, King of Paladeum, Vercerius and Primexis, Grand Duke of Cassimer, Amiralga, Vettricia and Comaris, Grand Prince of Aincrad, Orlathio, Suvexis and Docrath, Duke of Isotita, Callisia, Sonaraem and Nazelvartis, Prince of Gomearath, Isteguma, Gihorn, Wallooroy, Exodia, Addenia, and Zixos, Supreme Commander of the Imperial Armed Forces, Head of the Archonis Imperial Family.

[The Wattleys]

His Majesty, The Honourable, The Gracious, The Fashionable
HM The Grand Duke
The Lord of Grovean
The Lord of Crooks Hill
The Duke of The Caribbean Sea
The Duke of The North Atlantic
The Count of Westbury
The Count of WestMoorings
The Count of Waterloo Town
The Count of French Bay

[Sardakhar]

By the Grace of the Almighty, His Excellency the President of the Republic of Sardakhar and the Democratic Republic of East Sardakhar, Grand Duke of Maltinesia.

[Mrentec]

The formal title is "High President" but most just say "President".

[Bourbon Francia]

King of Francia and Navarre.

[Kvltway]

His Most Bloody Christ Raping Nefarious Imperial Satanic Highness, Third Ruler of the Most Brvtal Satanic Realms of Kvltway, the Trvest of the Trve, Blakk Metal Legend, Master of the Gibson Les Paul, Headbanger Supreme, Antipope Supreme of the Kvltwegian Satanic Order, Commander-General of Satan's Resistance Army and Basoon Virtuoso, Emperor Øystein II Necroporridge of the Aarseth Dynasty.

[Socialist Republic of Andrew]

God of Andrewism
Emperor Andrew
Baron Andrew
Oil Baron
Gold Baron
Archbishop Andrew
Archduke Andrew
Emperor of the Andrew Empire
Emperor of the SRA (Socialist Republic of Andrew)
God Emperor
Supreme Commander
Supreme Emperor

[Banusera]

Chief President of the Union Republics of Banusera

[Ertae]

The full title of the President is "His Excellency, [Name], President of the Executive, and Commander-in-Chief of the Armed Forces, of the Democratic Dominion of Ertae", though this form is rarely used anymore. He or she is generally introduced as "President of the Democratic Dominion of Ertae", referred to as "President" followed by his/her family name, and addressed as "Mister/Madam President".

[Berkenland]

Check my sig.

[Nicer potlimitomaha]

King Sitizen- The Proud Ruler of the country Potlimitomaha His Majesty King Sitizen

President Simit- The President of Potlimitomaha President Simit.

[Vetalia]

Praetor of the Republic of Vetalia formally, usually referred to simply as the Praetor. "President" is a completely acceptable equivalent albeit one that would mark the user as a foreigner or at least unfamiliar with Vetalian culture. The term dates back over two thousand years to the era of city-states and is a result of extensive Italic cultural influence during the period; the Praetors served as the supreme judicial and military leaders of the city states and the position was then retained after unification into the Vetalian Empire to refer to the highest ranking official outside of the Imperial family. After the Revolution it was retained as the term for the head of state, especially since he or she would also be commander-in-chief of the country's armed forces.

[Union Of Autocratic Empires]

Kaisar is Kaisar Karl (Raiss von Abula)'s main title, and the one he is usully referred as, is a play on the titles of "kaiser" and "caesar" (I know it's obvious for some people, I'm explainig it to those who don't get it).
His full title would be: Karl "the Sage" Raiss von Abula, Emperor of Abula, Kaisar of the Union of Autocratic Empires, Champion of the Unification War, Slayer of tyrants, Protector of The People, High Commissar, Destroyer of Religions, Patron of the Arts, Protector of History, Princeps of the Federal Council.

By the people, he is known as The Red Kaisar (due to his political leanings), The Lazy King (this is pretty self-explanatory), and Valkyria Chaser (based on the expression "amazon chaser", it was given to him by his marriage with Lady Sigbritt Väisänen, commander of the Valkyrian Guard (http://www.nationstates.net/nation=union_of_autocratic_empires/detail=factbook/id=404923) who, while only slightly more muscular than the average, is notably taller than him)

[Assamese Republic]

Historically, there have been MULTIPLE titles, but here are the main ones.

Imperial Era - Grand Czar of All of the Assam
Elected Imperial Era - Imperator of All of the Assam
The Fascist Era - Heismarkev jei Assam
1st Republic - President
Socialist Era - Commissar
2nd Republic - President

[West Jewistan]

Her Majesty, TalXGalXDekal Meartsi

[Apple-Loosa]

The Glory of the UDA, Hellina Intina, Leader of the Union.

[Regias]

Supreme Commander of all Regiasian Armed Forces, Lord and Master of the new colony of Anauros (Formerly known as the nation of Maxtopia), Defender of Regias, Grand Master of the Knights of The Platinum Cathedral, Commander of The Armed Republic of Regias, Aurelius Gaius Marius, First of His Name.

[Greater Mackonia]

His Excellency, Premier of the Republic of Greater Mackonia, Commander of Her Armies and Defender of her Peoples.

[Arlenton]

The President of the Republic of Arlenton

[Lairendor]

His Excellency Thomas Aurelius, Prince of the Commonwealth

[The Nazi Regions]

Führer

[Gonalla]

Empress of Gonalla, High Gonallan Sentencer, and Bureaucratic Coordinator; Andreanna the Great
(typically followed by exclamation points, but not in hyper-formal contexts)

[Eranshahir]

Head of State: X, King of Kings, Light of the Aryans, and Head of the Warriors (X, Shahanshah, Aryamehr, ye Bozorg Arteshdārān)
Head of Government: Prime Minister X of Eranshahir.

[Pontacium]

Supreme Dogtator for Life Endryu Metlok

[French Realms]

Emperor of the French Realms