I have 3 MAIN rulers that I LOVE to use, and they are:
O'Lipfa (they have a lip to help keep them straight on the cutting mats).
Sizes are:
3x18
5x24
4x36
These are the #1 TOP go to rulers that I use in fact I have 3 of the 18"
that I keep near me at all times.
I also have a 6x12 that I use sometimes.