1. Complete Information About your Phone
*#*#4636#*#*
  This code can be used to get some interesting information about your phone and battery.It shows following 4 menus on screen:
*. Phone information
*. Battery information
*. Battery history
*. Usage statistics
2. Factory data reset
*#*#7780#*#*
This code can be used for a factory data reset . It'll remove following things:
*. Google account settings stored in yourphone
*. System and application data and settings
*. Downloaded applications
It'll NOT remove:
*. Current system software and bundled application
*. SD card files e.g. photos, music files, etc.
Note: Once you give this code, you get a prompt screenasking you to click on "Reset phone" button. So you get a chance to cancel your operation.
3. Format Android Phone
  *2767*3855#
Think before you give this code. This code is used for factory format . It'll remove all files and settings including the internal memory storage. It'll also reinstall the phone firmware.
Note: Once you give this code, there is no way to cancelthe operation unless you remove the battery from the phone. So think twice before giving this code.
4. Phone Camera Update
*#*#34971539#*#*
This code is used to get information about phone camera. It shows following 4 menus:
*. Update camerafirmware in image (Don't try this option)
*. Update camerafirmware in SDcard
*. Get camera firmware version
*. Get firmware update count
WARNING: Never use the first option otherwise your phone camera will stop workingand you'll need to take your phone to service center to reinstall camera firmware.
5. End Call/Power
*#*#7594#*#*
This one is my favorite one. This code can be used to change the " End Call / Power " button action in your phone. Be default, if you long press the button, it shows a screen asking you to select any option from Silent mode, AirPlane mode and Power off.
You can change this action using this code. You can enable direct power off on thisbutton so you don't need to waste your time in selecting the option.
6. File Copy for Creating Backup
*#*#273283*255*663282*#*#*
This code opens a File copy screen where you can backup your media files e.g. Images, Sound, Video and Voice memo.
7.  Service Mode
*#*#197328640#*#*
This code can be used to enter into Service mode. You can run various tests and change settings in the service mode.
8. WLAN, GPS and Bluetooth Test Codes:
*#*#232339#*#* OR *#*#526#*#* OR *#*#528#*#*            - WLAN test (Use "Menu" button to start various tests)
*#*#232338#*#*                  - Shows WiFi MAC address
*#*#1472365#*#*                - GPS test
*#*#1575#*#*                     - Another GPS test
*#*#232331#*#*                 - Bluetooth test
*#*#232337#*#                    - Shows Bluetooth device address
9. Codes to get Firmware version information:
*#*#4986*2650468#*#* - PDA, Phone, H/W, RFCallDate
*#*#1234#*#* - PDA and Phone
*#*#1111#*#* - FTA SW Version
*#*#2222#*#* - FTA HW Version
*#*#44336#*#* - PDA, Phone, CSC, Build Time, Changelist number
10. Codes to launch various Factory Tests:
*#*#0283#*#* - Packet Loopback
*#*#0*#*#* - LCD test
*#*#0673#*#* OR *#*#0289#*#* - Melodytest
*#*#0842#*#* - Device test (Vibration test and BackLight test)
*#*#2663#*#* - Touch screen version
*#*#2664#*#* - Touch screen test
*#*#0588#*#* - Proximity sensor test
*#*#3264#*#* - RAM version