Oh man...I have huge library of underground comics and valuable collectible books worth change not to mention all my artwork, negatives and slides and photos and photo and sound equipment. and my biggest nightmare always seems to entail flood or fire. Luckily the flooding was isolated to the front of the apartment my parents bedroom, kitchen, bathroom dining room and front hall. When we finally got it fixed as they were putting finishing touches to the laundry room off the front hall someone found mold in the closet that came from the neighbors flooding earlier that spring. I had to have my closet and laundry walls removed, professionally dried and creosote treated, re-drywalled and painted (at the neighbor's expense thankfully).  What a bad year.
So I HATE FLOODING!  :)