For humor:
* "I'm so hungry I could eat a horse!" (You obviously wouldn't eat a horse.)
* "My backpack weighs a ton." (It's probably heavy, but not literally a ton.)
* "I've told you a million times to clean your room!" (You probably haven't said it a million times.)
For emphasis:
* "I'm so tired I could sleep for a week." (You probably won't sleep for a week, but you're emphasizing how tired you are.)
* "The line was a mile long." (The line might have been long, but not a literal mile.)
* "It's freezing outside! I need to wear ten sweaters." (It might be cold, but you probably don't need ten sweaters.)
For a rhetorical effect:
* "I'm drowning in homework!" (You aren't literally drowning, but the phrase conveys the overwhelming feeling of having a lot of work.)
* "The traffic is moving at a snail's pace." (Traffic isn't literally moving as slow as a snail, but the phrase emphasizes how slow it is.)
Note: Using exaggeration effectively depends on the context and your audience. Too much exaggeration can sound insincere or even silly, so use it sparingly and thoughtfully.