Shred of Doubt by Jo-Ann L & Vickie Moseley

This is an all-time favourite fic that I was reminded of recently.  I just love the characterisation embraced by these two long-standing XF fanfic authors: Mulder is constantly tortured but still tries to play at Alpha Male -being very possessive of Scully whilst feeling threatened and vulnerable, Scully is caught between Mulder and the rest of the civilised world, Kresge is an overbearing sexist pig, Maggie is the all-knowing peacemaker, and Bill Jr is at his belligerent, blustering best.  This all adds to the humour and makes this case file an extremely entertaining read.