Code for Andriod

*#*#4636#*#*
This code brings you some interesting information about your phone and battery.

*#*#7780#*#*
This code makes a factory data reset. It resets the google account data in your phone and removes all the downloaded applications.

*2767*3855#
This code can be used for factory format . It removes all files and settings from the internal memory. It reinstalls the phone firmware.
Think twice before applying this code as there is no way to cancel it.

*#*#34971539#*#*
This code displays information about your phone camera.Do not select any option from the list as this can remove the camera firmware.

*#*#7594#*#*
This code can be used to configure the 'End Call/Power' button action. By default,long pressing the button shows a screen with options -Silent mode, Airplane mode and Power off.
You can configure direct 'power off' on this button.

*#*#273283*255*663282*#*#*
This code pops up a File copy screen where you can backup all your media files like Images,Sounds,Videos and Voice memo.

*#*#197328640#*#*
This code gives you access into the Service mode.

*#*#232338#*#*
Shows WiFi MAC address.

*#*#1472365#*#*
GPS test.

*#*#232331#*#*
Bluetooth test.

*#*#232337#*#
Shows Bluetooth device address.

*#*#8255#*#*
launches GTalk Service Monitor.

Various Factory Test codes: 

*#*#0283#*#*
Packet Loopback. 

*#*#0*#*#*
LCD test. 

*#*#0673#*#*
Melody test. 

*#*#0842#*#*
Vibration and BackLight test.

*#*#2664#*#*
Touch screen test. 

*#*#0588#*#*
Proximity sensor test. 

*#*#3264#*#*
RAM version.

All the codes are tested and found to be working.