I found this......
I'M YOUR HUCKLEBERRY
On and off I hear discussions in which people speculate on the exact origin and meaning is of the quaint idiom used by Doc Holliday in the movie "Tombstone." I've heard some wild suggestions, including "huckleberry" meaning "pall-bearer" suggesting "I'll bury you."
Still others think it has something to do with Mark Twain's character, Huckleberry Finn, and means "steadfast friend, pard." This is unlikely, since the book of that title was not written until 1883. Tom Sawyer was written in 1876, but nowhere there is the term "huckleberry" used to mean "steadfast friend" or the like. Still others claim that a victor's crown or wreath of huckleberry is involved, making the statement "I'm your huckleberry" something like "I'll beat you!" But no such reference can be found in the historical materials supporting the use of this term in 19th century America. Additionally, "huckleberry" was native to North America so it's unlikely it was used in ancient Britain as a prize!
Solutions to such questions are actually very easy to find, since there are numerous dictionaries of the English language in its various periods, and there are dictionaries of English slang. These works simply cull from books, magazines, and newspapers of the period representative usages of the words to illustrate their meaning. I consulted several of these and found the expression to have a very interesting origin.
"Huckleberry" was commonly used in the 1800's in conjunction with "persimmon" as a small unit of measure. "I'm a huckleberry over your persimmon" meant "I'm just a bit better than you." As a result, "huckleberry" came to denote idiomatically two things. First, it denoted a small unit of measure, a "tad," as it were, and a person who was a huckleberry could be a small, unimportant person--usually expressed ironically in mock self-depreciation. The second and more common usage came to mean, in the words of the "Dictionary of American Slang: Second Supplemented Edition" (Crowell, 1975):
"A man; specif., the exact kind of man needed for a particular purpose. 1936: "Well, I'm your huckleberry, Mr. Haney." Tully, "Bruiser," 37. Since 1880, archaic.
The "Historical Dictionary of American Slang" which is a multivolume work, has about a third of a column of citations documenting this meaning all through the latter 19th century.
So "I'm your huckleberry" means "I'm just the man you're looking for!"