In the classic Western movie, Tombstone, Val Kilmer, as Doc Holliday, says to Johnny Ringo, “I’m your Huckleberry, that’s just my game.”
The saying is Southern and basically means, “If you want a fight, I’m your Man.”
It was Doc's way of saying that he's the man Ringo is looking for. When Doc goes on to tell Ringo he's "no daisy" after shooting him in a duel, Doc was saying "You aren't the best".
Then there's also a theory that Doc actually said "I'm your Hucklebearer" - which is another term for a pallbearer at a funeral.
"Huckleberry" is said to be the actual term for the final nail in the coffin at that time and the handles used to be called "huckles" - implying the idea that Doc is going to send Ringo six feet under.