Plaid, a block found in the perpetual calendar, 365 Quilt Blocks a Year by Nancy Martin, is drafted from a 5 x 5 grid.
It can also be found as #1827 in BlockBase.
Plaid looks like this when set side-by-side (a straight set):
I like it better with sashing and cornerstones. Some of the blocks have been rotated:
Small changes in color placement:
And the Plaid quilt block placed on point:
Sashing and cornerstones added:
Another color shift on the Plaid block in the center of the quilt, plus the addition of an alternate block and a plain block:
If I were to make the above quilt, I might redraw the alternate crossing block so that the seams match the Plaid block.
I thought I was gonna be bored with this block. Turns out that I was wrong! There are more Plaid designs to play with in my Electric Quilt file.