For some reason: Lake Trasimene
Obviously its an expert ambush. Hannibal manages to use an entire army to ambush another entire army and essentially obliterates it. I mean just being able to hide an entire army in ambush in the middle of the night after a long march just shows how disciplined and skilled all these men were who all spoke different languages and were from different cultures.

A note on pre-battle manoeuvre: Hannibals army had just finished marching through some disgusting Italian Arno river swamps where thousands died from disease and exposure. The men were so exhausted that some simply just collapsed. To steal some sleep, soldiers had to rest on top of dead mules or horses that had themselves died and were floating in the swamps. By this point, Hannibal completely understands the Roman mindset and their willingness for aggression and decides to use it to his advantage: There is a consular army stationed around modern day Arezzo, and instead of marching straight at it to give battle, Hannibal decides to march South-South-East and brushes past it to get their intention. As expected, the Romans follow to give battle. Thats when Hannibal leads the enemy practically by a leash. Towards sunset, he goes on the highground and begins making the appearence that their army is making camp to rest for the night and the Romans follow suit. Meanwhile, the entire "Carthaginian" Army is led behind the mountains and hills into ambuscade to prepare the devastating ambush they will launch the next day all along the road that they know the Romans will march on. Thank god they had the early morning fog.

tldr: tactical masterpiece and Hannibal deserves his praise.