gistfile1.txt

Vim Tips:

**g-**

There are a lot of better answers already given (".", "*", and "%" are far more useful), but I vote for "g-" because it is relatively new and feels like magic.  Somehow, it always seems to go to the exact text state I want.

Basically, if you make a lot of edits, then undo them, then make one more edit, then decide you want the first set of edits back, most editors can't do it.  Emacs can, but it's a pain.  g- in Vim will usually take you straight there.  {not in Vi}