Conditionally apply CSS class to a conditionally-rewritten View field? [This will require some background explanation.] We have a View (D7) displaying a custom content type. Flag Lists provides the option to select items via checkboxes and add them to a personal list. However some items are excluded from being available to add to such lists, and that it established by a boolean checkbox ("allowed" if checked) in the creation of the node. If NOT checked, the Flag List Operations checkbox in the View is rewritten by something else – currently, replaced by a simple text "X". 

Now we want to provide a tooltip message explaining why this item is not available to be selected – using Tipsy, Q-tips or something like that. To display such a message only for the ones where the checkbox has been rewritten with X or something else, I believe it needs to have a unique class that also applies to all other such instances. SO: Is there a way to make those instances have a unique class so they can trigger the tooltip message only when it's relevant?
Generally, every field has a unique selector already. If the defaults are not giving you enough control, I would recommend the Display Suite module which will allow to you add classes (and many other things) to individual fields. 

You might also be able add the tip with the same method that you are using to rewrite with the X right now.