George Washington: {Financial & Organized}
Definitely weak and peaceful leader, but I've seen him catch up from dead last in score to 3rd by just building peacefully. He also keep up with the tech race fairly well even though he had the smallest empire.
Franklin D Roosevelt - {Industrious & Organized)
Stronger then Washington, though they share similar personalities.
Arabs -
Saladin - {Philosophical & Spiritual}
In the games I've had him, he usually does pretty well throughout the whole game. He's advanced technologically but also has a lot of enemies.
Aztecs -
Montezuma - {Aggressive & Spiritual}
A complete nuts. Impossible to befriend and never lives pass middle ages. He tends to do very well at ancient and classic ages with a large empire, huge army, and fairly advanced technology. Beyond the middle ages his empire usually crumples to failed diplomacy and swallowed up by the AI and me.
Barbarians -
I've seen infantry from these guys, but never Mech Inf. They are free military academy for me to train my troops during peace time.
China -
Mao Zedong - {Philosophical & Organized}
Isolationist and poorly cultured. But even with all his cities threatened culturally, he manages to say within the tech race.
Qin Shi Huang - {Industirous & Financial}
Haven't play him much since 1/2 the game I played, I used him.
Egypt -
Hatshepsut - {Spiritual Creative}
Gotta say something about this AI. She definitely had the strategy part of this game down. In one game she chopped rushed over 100 horse archers in an attempt to bring me down (over the 2000 years). Needless to say I had a very hard time that game when couple with her bringing Qin into the war whom I blockade down to 3 grassland cities. Eventually once the chop rush steam runs out, she's a pushover. In another game I had Hats, Alex and I in an alliance against Monte. All 4 nations were in the top of the score chart and comparable in terms of military strength, tech, and land area with Monte having a slightly larger army. Both Alex and I did very well at whooping Monte's army and actually manages to capture a few cities, but the Egyptian front crumples really fast. Later on she declare war on Monte again twice. Despite having technological and land area advantage, Hats lost both war and drop down to one of the dead last AI scores. What I can conclude is that Hats has the mind of a brilliant strategist but a total idiot when it comes to tactics.
England -
Queen Victoria - {Expansive & Financial}
She can definitely tech. Vic manages to keep up in tech with me despite having 5:1 land ratio and most of my cities were developed well up to the late industrial age.
Queen Elizabeth - {Philosophical & Financial}
All I can say is she techs even faster then Vic
France -
Louis XIV - {Creative and Industrious}
Very high culture builder. I usually stack multiple religions and build churches on his border.
Napolean - {Aggressive & Industrious}
I've seen him build a lot of wonders and kept a small military and very little expansion, but that's a rare case. He's usually aggreesive.
Germany -
Frederick - {Creative & Philosophical}
He can tech pretty well with Great People up to industrial age, then he'll use Panzers to crush you.
Bismark - {Expansive & Industrious}
Haven't met him much.
Greece -
Alexander - {Aggressive & Philosophical}
Big opportunist, he picks on the low military strength civ. Anytime you find yourself below the average army size in the statistics, you can be sure he'll attack you soon. If you keep a relatively good military and share a religion with him, he makes a good ally and obidient dog.
Inca -
Huayna Capac - {Aggressive & Financial}
Financial trait makes him an dangerous tech-er. He never fully utilizes his UU, but by early industrial age, he usually comes in top 3 score if left unchecked.
India -
Mahatma Gandhi - {Industrious & Spiritual}
I love having him in my game. Though I sometimes feel pitiful for his watery eye, I alway have the pleasure of uniting the two civilization

.
Asoka - {Organized & Spiritual}
He does make a lot of cottages, but he's not that aggresive. Though he is a contender for the space race.
Japan -
Tokugawa - {Aggressive & Organized}
Complete idiot. He's a waste of such good trait combo and good UU. I have never seen him declare war on someone.
Mali -
Mansa Musa - {Financial & Spiritual}
This guy will trade anything, even if you backstabbed him multiple times and he's furious at you, he'll still trade his underware (or some very advanced tech) for something you have. Best AI to bully around and still maintain a talking relation.
Mongolia -
Genghis Khan - {Aggressive & Expansive}
I play the mongols a lot, so I haven't met him much to determine his personality.
Kublai Khan - {Aggressive & Creative}
Same as Genghis.
Persia -
Cyrus - {Expansive & Organized}
If there's anyone you can ignore and still get by, Cyrus is the man. Doesn't matter if your relationship is friendly or furious, he won't do anything

.
Rome -
Julius Caeser - {Creative & Expansive}
Another aggresive AI. He's even worse then Alex since he'll backstab you even if you have friendly relationship and stronger then he is. Another thing is that he makes ridiculous demands whereas Alex and Genghis's demand and aid requests are more on the reasonable side.
Russia -
Catherine - {Creative & Financial}
One of the best builder I've seen, she's also capable of fast expansion also. I had a game where she has 5 costal cities and 2 inland cottage farms all producing around 200 breakers. Needless to say she keep with in science with me even though I own close to 50% of the land mass.
Peter - {Expansive & Philosophical}
Haven't seen him much, and even in the games he played, he doesn't raise my alarm to be someone of importance.
Spain -
Queen Isabella - {Expansive & Spiritual}
Very annoying personalities. She's makes outrageous demands and usually have quite a few friends to back her up. She also gets angry easily.