*#06# Check IMEI no, by typing this code.
*#0*# Service menu will open for your new Android Phone
*#0228# Will show the battery status.
*#9090# / *#1111# Makes your device in Service mode.
*#*#4636#*#* For the information of battery, usage statistics and device.
*#*#34971539#*#* Provides Information about camera.
*#12580*369# Information about software and hardware.
*#228# For Analog-to-digital conversion Reading.
#7353# Hides test menu to Self Test Mode.
*#*#273283*255*663282*#*#* This code will backup all of your media files.
*#*#232338#*#* To see the WIFI mac address.
*#7465625# View the status of locked phone.
*#*#3264#*#* Check your RAM version.
*#*#44336#*#* Display build time and change the list number.
*#*#232337#*# This code shows you, your device’s Bluetooth address.
*#*#197328640#*#* Enables test mode for service.
*#*#8351#*#* Enable voice dial mode.
*#*#8350#*#* Disable the voice dial mode.
*#*#0842#*#* Test the Back-light vibration.
*#*#2664#*#* Test the touch-screen.
*#*#0289#*#* For Audio test.
*#*#0*#*#* For LCD display test.
*#*#232331#*#* Test Bluetooth of any Android device.
*#*#0283#*#* Perform a packet loop-back test.
*#*#1575#*#* For advanced GPS test.
*#*#1472365#*#* Perform a quick GPS test.
*#*#0588#*#* Performs a proximity sensor test.
*#*#7262626#*#* Performs field test.
*#*#232339#*#* Test Wireless LAN.
*#9090# Diagnose configuration of device.
*#872564# Controls U-S-B logging.
*#9900# System dump mode.
*#*#7780#*#* Reset to factory state.
*2767*3855# Formats Android device.
*#*#7594#*#* Change power button behavior enter this code.
*#*#8255#*#* Google Talk service monitor will be launched.
NOTE: Some of them may not work on your smartphone it all depends upon which brand and software you are using. If you got any codes share them with us.