Literally. Adverb. In a literal manner or sense: exactly.
Incorrect uses:
"I am literally buzzing for this party tonight."
You are not. If you were literally buzzing you would likely have a health problem that required immediate medical attention. It would also be hard for you to hold your drink.
"It is literally pissing it down."
Ew. Is that how you think the rain works? Sure, some of it probably is urine that has been evaporated and is falling back down into your eyes, but for the most part it isn't.
"Last night was wild. I'm literally dead today."
Someone should probably call the police. It's handy that you're still talking though; it will make for a solid witness statement.
"She is literally a goddess."
She's literally a human being. Whether she has the mystical powers of a deity or not will only be revealed when she is ready for us to see it. Let's worship her anyway, just in case.
Correct uses:
"You're literally using the word 'literally' wrong. People are literally laughing at you. You should literally stop."