Dupe Eliminator is provided by Salesforce Labs without official support. It may find and merge duplicate standard and custom objects.
Although it’s easy to install, I need to manually modify Visualforce page security and object permission in profile for user accounts with a custom profile.
Modify Page Security
[Setup]→[App Setup]→[Installed Packages]→[Dupe Eliminator]→[View Components] to see what has been installed with Dupe Eliminator. There are two Visualforce pages: MergeRecord and SearchMerge.
[Setup]→[App Setup]→[Develop]→[Visualforce Pages] find above two pages. Click on [Security] next to the page. Add custom profiles from Available Profiles to Enabled Profiles.
Profile Object Settings
[Setup]→[Administration Setup]→[Manage Users]→[Profiles] and click on one custom profile. [Object Settings]→[Dupe Eliminator]→[Edit] to change Tab Settings to [Default On]
Now, user may see [Dupe Eliminator] tab in [All Tabs].
Custom Merge Duplicates Button
It’s well written in P.12 of Dupe Eliminator (v1.5) – User Guide. The key is to use URL trick.
As a List Button:
As a Detail Page Button:
Detail Page Button example: