I think my least favorite was a gift from my Secret Pal - one of those 'rulers' with the slits in them for cutting strips. It may be June Taylor, not sure. I don't know why, but I just couldn't get the hang of it. Other than my rotary cutters, I think my favorite is my 8.5" wide Omnigrip (yes GRIP, not grid :wink: ) ruler. I use it all the time :D
And speaking of seam rippers, I just got a "scalpel" seam ripper & it works like a charm!