I found this thread really fun to read,
Fess Up! What Ruler Did You Buy? , but let's follow up with what is your
favorite specialty ruler?
I know you only really need a square ruler to quilt, but the specialty rulers are a lot of fun! I use my Simple Folded Corners ruler by Doug Leko all the time. The diagonal lines are perfect for trimming HST. I seem to always be making Dresden Plates and I love the extra large Dresden Ruler by MSQC.