Contacts Cleaner analyzes, reports, and fixes dozens of problems with Address Book and Apple Sync Services—problems ranging from the obvious, such as duplicated contacts, to the subtle, such as invalid characters and poorly formatted contact names.
Your contacts are the center of your personal social network, and as such are often synchronized among your Mac, your iPhone, and many other apps, services, and devices. Contacts Cleaner finds and fixes the little problems that can creep in while you're not looking.
Note: Contacts Cleaner currently does not fix contacts hosted on an Exchange server. Contacts Cleaner does work with iCloud.
For more information, tips, and a FAQ, see:
http://spanningtools.com/mac/contacts-cleaner-help.html