For squaring up HST the best ruler yet is the Quilt In A Day triangle square up ruler. You only make one cut. It is amazing. You place the line for the size you need on the stitching line of the triangle before you open it. One cut and you have a perfect squared up HST.
If you have a coupon at Joanns you can get it for around 9 dollars. Joanns marks up the price to 15 dollars but it is 11 at my local quilt shop. Who do they think they are fooling?
Like every one says the 6x12 or 6x24 is the most used
I have a June Taylor shape cut but have not used it. You need to fold the fabric to fit the ruler first so just havnt done it yet.
A 6 1/2 and a 12 1/2 in square up ruler is nice to have.
I love the turn table also.
Good idea about getting Joann coupons.