The classic example is the git unstage alias:

[1] ~/grocery (master) 
$ git config --global alias.unstage 'reset HEAD --' 

With this alias, you can remove a file from the index in a more meaningful way, compared to the equivalent git reset HEAD -- <file> syntax:

[2] ~/grocery (master)
$ git unstage myFile.txt

Now behaves the same as:

[3] ~/grocery (master) 
$ git reset HEAD -- myFile.txt