My entire home is my Femme Cave but I have some pretty specific spaces that are super mine.
I converted one of our bedrooms into an office/craft space and I LOVE spending time in there in my little "me-cave".
Jackhammer painted the walls a deep aubergine:
and it's trimmed out with a cool cream:
She also laid a gorgeous industrial floor in fireside oak:
My cave is a combination office/craft room/sewing space/geek nest. There is a long industrial restaurant table and lots of shelves and Jackhammer reworked the closet in that room by putting lots of deep shelves from floor to ceiling.
I also found a really huge (and heavy!) lateral file at a yard sale for $10 (brand new!!!) and it fit nicely under the shortest shelf in the closet. It made it really nice for organizing all of my papers and it locks! WEE!