The difference between one letter or two letters; writing with a "SHINUI" (not the usual manner).
One letter on top of another letter.
using magnets and loose leafs on Shabbos;
Important Guidelines for Dealing with Lice or Nits on Shabbos, and What to Do if One Finds a Badly Wounded Animal;
Part #1. Pulling off a hanging thread from a jacket, socks, etc., and removing a loose button;