Rulers and templates.
How many do you have? I have too many. Yes, I succumb to the latest gadget to make my life easier. But, do I really use them? For the most part, yes, I do.
When I first started quilting, there were no rotary cutters or neato acrylic rulers. We used Pellon and cereal cardboard to make templates. I still have some of them from the very first Log Cabin Quilt (pillow) I made.
I really like the rulers by Creative Grids. They have built in gripper dots, the lines are clear and easy to see. One downside, my quilting studio is so well lit, sometimes I have a bit of overhead glare, but nothing that I can't deal with. My fav ruler right now is the 8-1/2 by 24 inch. I have a 6-1/2 inch square that is totally gridded out with 1/8-inch lines. Love that one. Wish they still made it.