Not Tonight, Honey and Taming the Devil by Slaymesoftly
https://www.fanfiction.net/s/9358828/1/Not-Tonight-Honey-and-Taming-the-DevilTwo ficlets written for Schmoop Bingo prompts. AU season 4, Spike shows up wanting to fight Buffy to celebrate their "anniversary". She's sick and tells him to get lost. In the second fic, he finds her a few days later, they have a very short fight, and find out there's an attractions between them they weren't expecting... Complete
Lots of Slaymesoftly fics have fluffy mixed in with some angst at times.
This story I haven't read all the way through yet. It's really fluffy and takes place in Season 4. It was just completed.
Let It Snow by Annamonk
https://www.fanfiction.net/s/9912528/1/Let-It-SnowSummary: Just a little bit of fun for all my wonderful readers. Thanks for the feedback. You make me a better writer. I hope you enjoy this bit of fluff. In this tale, Spike and Buffy have to venture north at Christmas time. Complete
Swerve by Shadowlass
https://www.fanfiction.net/s/3811463/1/SwerveThis a one shot and fluffy.
Summary: When Willow's "will be done" spell is broken, Buffy and Spike immediately end their engagement. To the horror of the Scoobies, that's the only thing they end. Spoilers for Something Blue and This Year's Girl.
So Mote It Be by Ultrawoman
https://www.fanfiction.net/s/2098598/1/So-Mote-It-BeSummary: AU Season 4 - During her Will Be Done spell Willow doesn't mention Buffy and Spike getting married, instead she complains about their childish behaviour...Oops! How exactly will the gang cope with the effects? Complete
Childhood Trauma by Ultrawoman
https://www.fanfiction.net/s/2395240/1/Childhood-TraumaSummary: This is the sequel. Almost a year after 'So Mote It Be' around 'Real Me' now Dawn is sick of being treated like a kid, and wishes her sister and the Scoobies could understand how she feels. On the Hellmouth, sometimes wishes come true... Complete
This one shot is new and fluffy fun. I wish there was a sequel.
Tis the Season by Behind Blue Eyes
http://spikeluver.com/SpuffyRealm/viewstory.php?sid=37359Summary: Set in Season 4, Buffy and the gang are quietly celebrating the holiday season. Throw in an naughty impromptu roommate and an even naughtier sweetened beverage, and the Scoobies get far more than they were bargaining for.