Little Black Sambo is a dergoitory term for an african american whom one finds as weak, or physically inferior yet also of black heritage. Also was a small african child featured in a Looneytoons cartoon for when Looneytoons was still good.
Little black sambo is also one of the best comebacks to "Whiteboy" you aren't expected to say anything other than blackboy as a comeback but when you pull the LBS they have no idea what you say. Best used if followed by a British explorer accent to humor them to prevent an assault, similar to what Wild Bill said in the Green Mile.
Black guy: Hey, White boy!
White guy: Little black sambo.
Black guy: What???
White guy: (Strong english accent) Yes sir, yes sir! How do you do?!