"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!"

In Texas Hold 'Em, one who often catches the card that they need on the last card dropped (the River). If this happens often enough, they live on the "river," just like Huck Finn.

an ignorant country person, a bumpkin, a rube, someone ripe for the picking. When you encounter one on the road you say, hi Huck. Hence the name of Twain's character.

Means a backwoods, six toed, inbred yankee who was denied admittance to the American south.

from the latin phrase 'huckleberry hound' this means pound, as in £1.

what once started as just a fuck buddy but turned into the best sex you ever had so he's/she's a keeper AKA huckleberry !!

An person who, owing to weakness other inferiority, is forced to become another person's bitch.