Some of my favorites are:
"You see, I had this space suit." from Have Space Suit Will Travel by Robert A. Heinlein.
"Marley was dead: to begin with." from A Christmas Carol by Charles Dickens
"O for a Muse of fire, that would ascend The brightest heaven of invention, A kingdom for a stage, princes to act And monarchs to behold the swelling scene!" from The Life of King Henry the Fifth by William Shakespeare.
That's why I try to craft a first line that hooks a reader, one that says, "Keep reading to find out more." Here's a few of mine that I've created:
"She almost stepped on him, she did in fact, because the moan was what startled her."
"Dr. Alex Jernigan lifted the top of the alien sarcophagus up and away from the jeweled interior cavity to get a closer look at the unquestionably human body inside."
"Cory stopped on the midway, the crowd flowing around him like a vast walking, talking river as he turned in a slow circle. "
Do you have a favorite first line that hooked you in right away?