The most striking difference between Huck and Tom in this novel is the difference in their senses of practicality. Huck has a more "mature" imagination in that he strives to use his imagination to solve problems. Tom, on the other hand, uses his imagination to create problems. Huck wants to be pratical. Tom wants adventures. Hence, we might use titles like, "The Problem Solver and the Dreamer" or "The Problem of Practicality" or "Practical and Impractical Imaginations".
It is, indeed, challenging to give you a title that points to the comparisons and differences between the two personages of Mark Twain's works that you have made without having read your essay. However, if you are merely looking for a more generic title, what about something like this that has a play upon the nom de plume [pen name] of Samuel Clemens as well as a play (pun) upon the old expression "Never the twain shall meet":
Tom Sawyer and Huckleberry Finn: The Twain Meet in the Imagination of Samuel Clemens
Wow! The mind reels! Stolperia has it right that, without knowing more about your essay, we can't help too much with an exact title. I'd be happy to give you a few humorous ideas, though, that could help get a laugh from your audience (the teacher?) and, therefore, give you some brownie points.
Considering your essay is comparing the two mischievous boys Huck and Tom (but not knowing how you are comparing them exactly), I'll focus on their boyish behavior. (In fact, if you take a look at my list and then think about some of the popular songs/shows/etc. between you and your friends right now, I'm sure you could come up with a title just as humorous, ... and probably more relevant than my ideas.) In the meantime, though, how about these:
Smokin' in the Boy's Room
Hangin' with my Peeps
In the Hood (of the Mighty Mississip)
The Backstreet Boys
Monkeys Jumpin' on the Bed
I've Got Friends in Low Places
Keepin' It on the Down Low
Do you already have your compare and contrast essay for Tom Sawyer and Huckleberry Finn written? If you do, go back through what you have written and find your title there. What is the main point of your comparison? Are you focussing on the difference in family background and how that affected the way in which the two boys looked at life? Are you emphasizing how the differences between Tom's school education and Huck's self-taught knowledge shaped their experiences? Are you highlighting the caring and respectful characteristics that are in both of their characters, however deeply it might seem hidden at times? Are you contrasting how the actions of those around them influenced their lives and decisions? By reviewing the points made in your essay, you should be able to identify a major theme or pattern that can serve as a basis for your title.