1.
Diagonal Seam Tape from @cluckclucksew. I've tried a variety of tools to get accurate 1/4" seams and this has been the most effective for me. This tape is intended for diagonal seams such as for Half Square Triangles (HSTs) or Flying Geese but I use it for plain straight seams for very accurate results.
2.
Stripology XL Ruler from Creative Grids. Total game changer. Cut strips and pieces in a fraction of the time.