In Deja Q, Worf's response is legendary, and Q's comeback here is cute, making the below exchange my favorite:
"I have no powers. Q, the ordinary."
"Q, the liar. Q, the misanthrope."
"Q, the miserable. Q, the desperate. What must I do to convince you people?"
"Die."
"Oh, very clever, Worf. Eat any good books, lately?"
"I have no powers. Q, the ordinary."
"Q, the liar. Q, the misanthrope."
"Q, the miserable. Q, the desperate. What must I do to convince you people?"
"Die."
"Oh, very clever, Worf. Eat any good books, lately?"