Huck Finn means a lot of different things to a lot of different people. Most of the adults in St. Petersburg think he's a menace to society; he's "cordially hated and dreaded by all the mothers in town" (6.43). The kids, on the other hand, wish "they dared to be like him" (6.43). Huck is happy to accompany Tom on almost any adventure, but here's the thing: Huck, despite his reputation, never really has much of a say. He agrees to go to Jackson's Island and he helps look for treasure, but it isn't until the very end of The Adventures of Tom Sawyer – when he goes to the Welshman for help – that Huck really comes out of his shell.
So who is the real Huck? He certainly doesn't seem to be the "idle, and lawless, and vulgar and bad" kid the townspeople make him out to be. No, we get a closer look at Huck just after he and Tom have found Injun Joe dead drunk on the floor of the haunted room. After running away to a safe place, the boys say good night to each other:
[Tom:] "That's all right. Now, where you going to sleep?"
[Huck:] "In Ben Rogers's hayloft. He lets me, and so does his pap's nigger man, Uncle Jake. I tote water for Uncle Jake whenever he wants me to, and any time I ask him he gives me a little something to eat if he can spare it. That's a mighty good nigger, Tom. He likes me, becuz I don't ever act as if I was above him. Sometime I've set right down and eat with him. But you needn't tell that. A body's got to do things when he's awful hungry he wouldn't want to do as a steady thing." (28.31-2)
In this one moment, Huck reveals himself to be modest, vulnerable, and caring. He appreciates the help that he is given by Ben Rogers and Uncle Jake, and he does his best to repay the favor by helping to tote water when he can. He is embarrassed to admit that he associates so closely with a slave, but only because there is a social stigma attached. His response to Tom is so bashful and so guileless, it totally dispels the "bad boy" aura that surrounds him.
Huck character also develops a bit over the course of the book. He's torn up about the Muff Potter situation, and he's certainly tolerant of his fellow men; he simply has trouble taking action. With Tom's help, he learns to overcome his shyness and act on his virtuous impulses. This is the real Huck, if there is one. This is the Huck who will take Jim down the Mississippi in The Adventures of Huckleberry Finn.