My favorite is a battery operated mustache trimmer. If you need to remove a long seam (like recently when I stitched my two backing pieces in different directions...,) you simply turn the trimmer upside down, so it doesn't cut the material and run it along the seam! Took out a ten foot seam in about 60 seconds!! Works great for even the little mistakes. I suggest battery power because it is more portable than electric cord. About 18-20 dollars at any drug store or Walmart.