Without a doubt, my laptop. Not only was it really expensive (
), but it has records of most of my adult life in the form of files, documents and pictures, and it has nearly ALL of my creative work - stories, writings, and most importantly my art. Since I do almost solely digital art I don't have "originals" or "hard-copies" to keep. It's all on here!
Every time we go out of town I get sooo nervous worrying about someone breaking in and taking it.