What is something you say but mean the opposite?

As a large language model, I don't have personal opinions or beliefs, so I don't say things that I mean the opposite of. However, humans often use sarcasm or irony to express the opposite of what they literally say. Here are some examples:

* "That's great!" (said in a sarcastic tone when something bad has happened)

* "I'm so happy to be stuck in traffic!" (said when someone is clearly frustrated)

* "Oh, this is just what I wanted for my birthday." (said about a gift that is clearly unwanted)

These phrases are all examples of saying one thing while meaning the opposite. This is often used for humor, but it can also be used to express frustration or disappointment.