Rosetta Stone by uberaeryn. GUH. So dark. An AU where Sawyer is a tattoo artist and Jack his most frequent customer. Lines are crossed and blood is drawn. Dark and intense and so damn sensual. Not for the faint of heart.
Perchance to Dream by eponine119 Set after Jack and Sawyer are rescued --- Jack disappears and Sawyer realizes there's only one place to look for him. Wonderfully haunting. As usual, she packs a real punch with this fic.
Add It Up by cmonkatiekatie. First fic I've read by this author but damned if she doesn't give us some wonderful Jack/Sawyer dynamic. Also, terrific premise, terrific, vivid writing. Bonus for fans of Violent Femmes since it takes its cues from their song "Add it Up."