I don't read the book, so my historical knowledge of the characters are limited, but it's always been Gan Ning, Zhou Yu, and Ma Chao for me. Gan Ning is a pirate, pillaging villages and his bells alone would scare the daylights out of the people in the vicinity. He also struck a deep friendship with Ling Tong and the story of his death remains an enigma to me. On one account (which I remember most) is that vultures began to devour his corpse or gathering around it to protect it. Either way, I've been interested in him since DW2. Zhou Yu is your military intellect/genius, who is renowned for his looks and most importantly his adroitness in battle tactics. Ma Chao's sheer strength and superhero-like attributes is fascinating and never ceases to put up a powerful presence.
Ma Chao's moveset>>>>Zhou Yu's and Gan Ning's though.
Ma Chao sticking his spear to the ground and swinging on it is quite creative too