Okay hang on.... are we talking about piecing rulers or quilting rulers?
For piecing, if you really want a specialty ruler that has a ton of possibilities and a whole slew of patterns ready to go, I vote for the Sew Kind of Wonderful Quick Curve ruler. I've made 2 sample quilts for my LQS, the patterns are very well written and the quilts are fun to make.
For quilting, longarm or DSM, that really depends A LOT on what kind of quilting you like to do and what kind of quilting you want to learn to do. And your skill level. I do love Bethanne Nemesh's rulers, they are pretty "specialty".