Right-click is different from left-click

I consider this to be a common problem.

Sometimes I left-click on things. Sometimes I right-click on things. When I left-click I want one thing, when I right-click I want something else. Far too often, I find that the left-click makes sense and the right-click does the same as left-click. This is insane.

The rule of the week is:
Programs should do something sensible (and different) when users right-click. And what they do should be different than when users left-click.