Your title says before S1 or before so that is what I've listed. Obviously there are loads more S2 fics that are less AU. I haven't included any that are time travel do-overs that went back S1, just ones where S0-1 is the first time they have met...
Future Childe (sequel
Present Childe) by Ariel Dawn
Spike, on a hiatus from Dru's company meets a certain blond pre-slayer 15 year old and decides to keep her.Sideways by goldenusagi sequels Sideways Interlude and (wip) Tilted both also on here
Alternate reality. Buffy starts as a normal college girl. But her life is slowly turned upside down beginning with the day she's unexpectedly in danger. Hired by chance to protect her is Spike, a vampire with a reputation for doing business with anyone for enough money. She's less than thrilled, but finds herself drawn to him even as she realizes he's more than he seems. But humans aren't the only ones after her, and when she's called as the Slayer, her whole world changes. Things with Spike, who she's discovered some realities about, are no longer as simple as they seemed. But being sent to the Hellmouth and realizing the high death rate of her calling, Buffy hires Spike as backup with the only thing she has left—Slayer blood.Shattered Silence by the enemy of reality
Life, freedom, feelings. There was no place for them here. This was hell, and she its most valued possession. Buffy's life takes an unexpected turn after being kidnapped, and as the line between sanity and madness starts to blur, the opportunity of freedom will present itself. Will she find enough will to live to take it, or will she take the easy way out and give in to the pain consuming her soul? And what does one ruthless vampire thirsty for her life have to to do with all this? When their paths cross perhaps they'll both realize that love can appear when you least expect it.In Omne Tempus by Holly
For a hundred years, William the Bloody has led a trail of bloodshed and chaos across Europe and the Americas. That all comes to an end when the woman he's devoted his existence to brings his mate to him in the guise of a late-night snack. A small girl with eyes of green and blonde hair. And suddenly, Spike is thrown into a world of color beyond the black and white, and his life is never the same.Lost and Found by Addie Logan
Desperate to kill his third Slayer, Spike seeks her out – only to find she isn't exactly up for fighting. He decides to call a truce long enough to get her back into top form; however, he is soon reminded of just how unsuccessful his plans tend to be...You Think You Know What's To Come Pt2 by OracleHolly sequel
You Haven't Even Begun (I thought the sequel was a wip but it says it is complete on this link
Pre-BTVS, Buffy Summers has been having strange dreams... Broken Origin I by Dev Nine-Asher sequel (wip)
Broken Origin II (AU) L.A. 1996 - Spike, sans Dru, ends up Master of Los Angeles. One night his minions bring him a new pet - Buffy Summers, the new Slayer.An Eye For An Eye by Schehrezade sequel
Out of SightIn which we have a very different Spike, who for once has a plan and is sticking to it. Who appears just when The Three attack Buffy and the fic spins off from there in a very different direction.Animal I Have Become by Blood Faerie
A spuffy twist of the episode where Xander was possessed by a hyena. Instead, Buffy is possessed and who should wonder by but our ever-so sexy vampire, Spike! Love As A State Of Mind by Jeni and Kari Mouke
Say It If It's Worth Saving Me by Jerzeyanjel
Not only does the Hyena spell zap Xander but Buffy gets zapped too. What will happen to our slayer when she encounters the sexy blond vampire? Will this be the death of him? Or will she finally stake her claim on him?Teacher's Pet – Twisted Spuffy Style by bloodshedbaby
Ok, so the bug lady needed virgins, right? Well, what happens when Spike and Buffy are thrown into the mix? (Or into the basement with Xander and Blayne, if you want to get technical) Written for the Live Journal community Twisted Spuffy. Welcome to the Hellmouth? by Schehrezade
Spike, a curse, a Slayer and a Hellmouth – what more could you ask for? Written for the seven_seasons ficathon Set in Season One and spinning off canon pretty much from the first word – Spike ends up in Sunnyhell alone and subject to the whims of The Powers – what can a vamp do? How will he fit in? Will he fit in? Does he want to? What will Angel's reaction be to the presence of his Grandchilde let alone Buffy's reaction to the peroxide pest? A Future Set in Sand by Always_jbj
What if not all of the Master's childer mindlessly went along with his demands? Could the presence of a disgruntled Master vampire of the Aurelian line sway the course of a supposedly unbreakable prophecy? And what will that mean for the slayer who is fated to die by the Master's hand?Demon Dreams by spikesdeb sequel
Reality BitesA Spuffy rewrite of Season 1's 'Nightmares'. Odd things are happening in Sunnydale, people's worst fears are coming true. And Buffy's nightmares always feature vampires. Now who do we know who's a vampire? 
If I'm Not in Love With You by Tuesday Girl
Spike is sent to kill the slayer. However, he does the thing all demons fear, yet seem to do, he falls in love with her. But how will Buffy feel when she finds out that the love of her life is a liar.]Nothing To Fear by maryperk
VampBuffy sees a pretty man and decides to keep him. Set in Nightmares, Season One.Perchance to Dream by Kari Mouke
A season one bitey fic with a taste for mortality. Buffy/Spike MF NC17 sex, bloodplay, & violence.Puppets and Pawns by Ariel Dawn
A rewrite of the season one ep The Puppet Show Spike and Dru come to Sunnydale in search of a special something.The Secret Slayer by maryperk scenario #1 in The Immortal Guardian series
Something unexpected happens to Buffy on her first night in Sunnydale. Something that causes her to change her name and hide from the people that were to be her friends. What happens when a certain peroxide blond vampire rolls into town? 
