Common words:
* ex-husband/ex-wife
* ex-boyfriend/ex-girlfriend
* ex-employee
* ex-president
* ex-soldier
* ex-convict
Less common words:
* exacerbate (to make worse)
* exalt (to praise highly)
* exceed (to go beyond)
* exhale (to breathe out)
* exodus (a mass departure)
* exonerate (to clear of blame)
* exorbitant (excessively high)
* exoteric (easily understood)
* expedite (to speed up)
* expel (to force out)
* expend (to use up)
* explore (to investigate)
* expound (to explain)
This is not an exhaustive list, as there are many more words with the "ex-" prefix. You can find more by looking in a dictionary or thesaurus.