Even Fortunato's name is an example of situational irony because you would think that a guy who is named Fortunato is fortunate, but he is absolutely not.
This is an example of situational irony because although he is talking, he is not being sarcastic. Montresor is acting like he is the caring person. Also, when Montresor kills Fortunato, he actually will be responsible for his death.
"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. For me it is no matter. We will go back; you will be ill, and I cannot be responsible. Besides, there is Luchesi-"
"I drink, to the buried that repose around us."
This is an example of irony because Fortunato does not know that he will soon become one of the bodies buried down in the catacombs. Also, Montresor is meaning the exact opposite as what he is saying. He knows that Fortunato's life will be short and he will not live a long life.