My favorite example of verbal irony in "The Cask of Amontillado" comes when Fortunato is being led deeper into the catacombs and has to stop to catch his breath. After a long cough, Montressor slyly suggests that Fortunato give up the descent for the Amontillado because of his bad cold. Fortunato retorts that he
"... will not die of a cold."
" True, true," Montressor responds.
It is ironic, of course, because Montressor already knows how Fortunato will die later that night.
Another example comes when Fortunato asks Montressor if he " 'is a member of the brotherhood.' " Montressor assures Fortunato that he, too, is a fellow Freemason. When Fortunato requests the secret sign shared by all Masons, Montressor produces--not a secret sign--a trowel: a tool used by brick masons. " 'Surely you jest," Fortunato replies. Of course, it is no jest. Montressor had planned carefully and brought along the necessary tool for the job at hand.
The best example of verbal irony to be found in Poe's "The Cask of Amontillado" is in the fact that Montresor continually refers to the man he intends to murder as his friend, his good friend, and his poor friend. He has gotten into the habit of referring to Fortunato as his friend for several reasons. In the first place, he wants Fortunato to think of him as his good friend. In the second place, he wants everybody who knows them to think of the two of them as good friends. He wants everybody to think they are friends because when Fortunato mysteriously disappears, Montresor doesn't want anybody to have the slightest suspicion that he could have been connected with it. He knows that he is going to have to act concerned about Fortunato's disappearance for a long time because of his supposed friendship. He will keep asking questions about him? If there is a search, he will have to participate. If there is a reward offered, he will have to contribute generously. He knows that in order to make Fortunato and everybody else believe in this false friendship, he will have to believe in it himself. A good liar knows that he must believe in his own lies, and it is quite possible for an intelligent man to do this. He can't help referring to Fortunato as his friend throughout his narrative because he has conditioned himself to believing in their strong friendship.
There are many other examples of verbal irony in Poe's story. Another interesting one is where Montresor tells Fortunato:
"Come," I said, with decision, we will go back; your health is precious. You are rich, respected, admired, beloved; you are happy as once I was. You are a man to be missed...."
Montresor, of course, is using reverse psychology. He is also giving his victim a false assurance of his innocent intentions, because he would hardly be persuading him to go back if he were intentionally leading him into danger. But most importantly, Montresor is probably savoring the thought that he can destroy Fortunato's wealth, respect, admiration, and love with his fiendish plan; and furthermore, he can get the added satisfaction of inflicting pain on Fortunato's friends and family because Fortunato is a man who will be missed. Anyone who plans a murder must give some thought to the effect his crime will have on the victim's loved ones, and Montresor is evidently so sadistic, or so full of hatred, that he wants to punish Fortunato and everyone connected with him.