Overall? Charizard.
Even before Pokemon made its way across the Atlantic I was a fan. I've always been kind of a pyro, and I've always loved dragons.
I was in grade 5 when I opened up an issue of Nintendo Power which basically served as the launching of the Pokemon campaign in North America to build hype for the game(s).
I flipped through it, and I knew the game was a must have. On top of that they had pictures of all three starters and their evolved forms. The interest in fire plus the coolness of dragons drew me to Charizard.
After playing Pokemon since grade 5 Charizard's status as my go to Pokemon hasn't changed.
Not only does he look bad ass, he's easily the strongest of his type, and can hold his own against almost any other Pokemon. I've actually taken some powerful water-types to the limit and won with Charizard.
After Chairzard, despite my love for fire types, the my second favourite is a tie between Scyther and Nidoking.
I like Scyther because I think praying mantises rule. I like Scyther so much that I've resisted all urges to evolve him.
Nidoking just looks cool. Plus during my Red days he stuck on my team from the beginning, and due to his ability he never left. At some points he was stronger then my Charmeleon/Charizard. Plus, seeing as your rival always ended up with a Rhydon, Nidoking acted as my team's "horn" equivalent.
iplup 
:-*
