That's a hard question to answer. I have one favorite book that I find many great quilts, Leisure Arts Presents Encyclopedia of Classic Quilt Patterns. I think I counted 101 different quilts and I love so many of them. I've made several.
Other than that 1 book, I really have to hunt to find something that I 'want' to make. I'm about to the end of making quilts for my great nieces and nephews so I'm looking to find a quilt I love for me. That's hard to find these days although I've always wanted to make a sunbonnet sue or a fisherman fred.... and then there's the garden quilt I made in a mini size for a friend's new baby. I could make that one full sized. My DH loved that one and didn't want me to give it away. I designed it and I don't have a picture but I do have the original sketch that I drew. Maybe that's the one. Thanks for asking this, I think I've decided what to do next.