Richard Kettlewell

There are four possibilities when you click:

1. Nothing happens.
   
2. Window raised but object not selected.
   
3. Window not raised but object selected.
   
4. Window raised and object selected.

So there are 64 possible ways an object can respond to three mouse buttons.

Some examples:

• Folder in the Finder: click 4, ^click 4, ⌘click 4.
  
• Folder in Mail: click 4, ^click 3, ⌘click 3.
  
• Link in Safari: click 2, ^click 2, ⌘click 3.
  

I expect you can find objects which implement some of the other 61 possibilities.