I've accumulated a huge selection of rulers over the years. Handi-Quilter makes some really good ones, including the Versa Tool. I prefer rulers that are clear and etched with helpful lines. I do not like rulers with handles. The ruler I use most is a SITD ruler. I use it for SITD to stabilize a quilt, and also for straight lines within the blocks. I also use circles of different sizes, and clamshell rulers. If you have an opportunity to go to a big quilt show, take a class in longarm quilting with rulers. The instructor usually has a selection of the rulers that she sells and you can get an idea of how to use them and decide which ones you're most likely to use.