Black Bottle ~ "Easy as a, b, c, so count yourself lucky. 19-12-21-9-3-5-7-1-20-5-18-1-20-19"

By far the easiest. Anyone can figure this at lightning speed as it's easy enough even without the huge giveaway within the hint. You simply replace each number with the corresponding letter in the alphabet. Example: 1 = A or 17 = Q. When this is done correctly, you'll end up with

19-12-21-9-3-5-7-1-20-5-18-1-20-19 = S-L-U-I-C-E-G-A-T-E-R-A-T-S = Sluice Gate Rats
FFXII/Quests/Fishing - FFProject