OnyX is a simple but incredibly powerful maintenance and optimization tool for OS X. Note that this version is only for Mavericks.
Onyx is completely free and will help you keep your Mac clean and in perfect running order. The first time you run OnyX it'll verify S.M.A.R.T status of your disk to prevent failure and analyze the structure of your volume. Every action is well explained and OnyX also includes a help guide for anything you're not sure.
Pros:
Enables modifications on Mac OS X elements: OnyX (Mountain Lion) for Mac does a great job at bringing out the functions you may not know in Mac OS X. You can modify the Dock, QuickTime, Safari, iTunes, Mail, Spotlight, and the Log-in, as well as disable the creation of DS_Store files. You can also specify the format of the images saved during screen captures.
Comprehensive cleaning: The Cleaning function provides a quick way to clean the system and user cache, font cache, browser cache, system logs, automatically saved documents, temporary and recent items, and the Trash.
Automated system tasks: With this software you can automate maintenance, rebuilding, and cleaning tasks. These tasks include the repair of permissions, execution of maintenance scripts, display of folders' contents, cleaning of cache, and the rebuilding of Spotlight and Mail indexes.
Cons:
Dangerous for inexperienced users: Given the extent of system modifications it can implement, Onyx is not intended for those who lack the right know-how in changing advanced configurations. There are several warnings in the application, but there is no way to stop unintended changes. OnyX is a tempting tool for those who are trying to become advanced users.
Cannot be password-secured: If it's used on a shared computer and falls in the hands of inexperienced users, it may cause system problems.
Technical Details:
Name: OnyX 2.7.4
File size: 28MB
Price : Free
Developer: Titanium soft