This is a very very very simple application for WM5+ PPC / SP (CF2.0) I rustled up in response to a need to remove duplicate contacts on a device.

It is an EXE only (copy to your device and run), which has a basic GUI which allows you to scan for duplicates, and then choose (after being told your duplicate count) whether to remove them. Contacts are compared based on 'File As', field, 'Email' field and 'Home / Work / Mobile' phone fields. If all those fields match, it's deemed a duplicate.

The application scans about 200 contacts in under 2 seconds.