Select multiple options or only one exclusive

Question

I want to give the user a list of possible options to select with checkboxes. But what if I want him to provide a way to select only one without having to deselect the others?

Eg:
X  OptionA
X  OptionB
   OptionC
X  OptionD

I'm thinking something like "shift-click". If he shift-clicks OptionC, the other 3 automatically deselect.

Answer 1

Don't hide functionality in shortcuts.

If your user's work flow demands the need to quickly and easily deselect all options, make the option explicit. Provide a button that does what it says:

^{download bmml source – Wireframes created with Balsamiq Mockups}

Now it is clear to the user how to deselect everything they've selected. A click of the button and a click of "Option 3" gives them what they want. Easily.

Don't confuse system shortcuts

Shift-click has meaning in many systems and when dealing with lists. It will, often, select (or de-select) all items between the last selection and the item just clicked. Don't redefine a user's mental model of how that shortcut works.

Answer 2

As evil-closet-monkey already said: Don't hide functionality in shortcuts.

Here's another idea that might work:

The Link ist normally hidden and shows when the User hovers over the Text or the Textbox

The user can click on the link at the right and everything deselects except the one where he clicked the link.