6"x24" My favorite, by far
6"x6" 3rd choice
4"x14" 2nd choice
12"x12" for squaring up, which I do infrequently:>)
All are Omnigrid, because the yellow lines are easiest on these old tired eyes.
Now, having said that - I have a drawer full of rulers I just "had to have" but never (or maybe once or twice) used LOL