What are some first lines to novels/stories/fanfic that you like/that you remember off the top of your head? (Combining your first two questions because the answers tend to be the same.)
Who's there? - Hamlet (that is the best first line in the universe.)

In a hole in the ground there lived a hobbit. -- The Hobbit by JRR Tolkien (perfection is simplicity.)

It is a truth universally acknowledged that a single man in possession of a large fortune must be in want of a wife. -- Pride and Prejudice by Jane Austen (my sister read this for high school English, and remembers a boy who was loudly certain he was going to hate girly old JA, until they read the first pages out loud together in class, and he cracked up at line one and didn't stop laughing through the whole book. she got the kid for English literature hook, line and sinker.)

— Serve him right he got his muthafuckin face fuck'd, shudn't b callin me a Paki, innit. -- Londonstani by Gautam Malkani (I was hook-line-and-sinkered by this guy's prose.)

His two girls are curled together like animals whose habit is to sleep underground, in the smallest space possible. -- Animal Dreams by Barbara Kingsolver (ditto.)

To begin at the beginning:
It is Spring, moonless night in the small town, starless and bible-black, the cobblestreets silent and hunched, courters'-and-rabbits' wood limping invisible down to the sloeblack, slow, black, crowblack, fishingboat-bobbing sea. -- Under Milk Wood by Dylan Thomas

(I think separating lit and fic is spurious, but it was easier to hunt down links to the linkables all in a row. So:)
There's someone in the bed with him. -- A Howling in the Factory Yard by synecdochic (not technically the first line; the story opens with an excerpt from a mission report. this is the first line of the main narrative, and, in context, creepy as fuck.)

The fifth stall in the men's washroom at King's Cross station had had a "Closed For Repairs" sign on the door since 1973. -- Transfigurations by resonant8 (I adore Res' dry, conspiratorial humour.)

"I’m laughing so hard I think I’m dribbling a little," Malfoy said from under the table. -- Drop Dead Gorgeous by Maya (because it's hilariously potent characterization -- that Malfoy would say that out loud gives you quite a lot of information about Malfoy --and it neatly sets up a good opening question (what's so funny?).)

"Sooner or later, you have to face reality."

"... no I don't." -- Walked Right Out of the Machinery by rydra_wong (this is the entire opening section. after the line break, the narrative restarts. I found it a brilliant, almost epigraph-like hook, and was further floored by the fact that I could tell exactly who was speaking, with absolutely no context other than knowing the fandom. Rydra's character voices are that inevitable.)