.... developed 3 rolls and made 4 cutting mistakes last night - 3 were through a shot I didn't care about... the 4th...ARG!!!!
I keep cutting off tiny slivers of the next frame... I either need thinner bladed scissors or a slide mounting cutter...
Straight edge and a razor blade for sheet film. Any pair of scissors I can find for 120 -- though I wiggle the film advance a little to get a little more space between the images (Rolleiflex).
I use a pair of SS surgical scissors that have short blades only 2 to 3 inches long. Larger blades get in the way and block vision. You can also get suture scissors that have only 1 inch blades. Both are not very expensive.