These Android Secret codes are mostly universal, and should work on Android devices, no matter the manufacturer. There might still be carrier restrictions on certain codes though, so they're not all guaranteed to work.
Android Secret/Hidden codes 2015 :-
*#06# - IMEI (International Mobile Station Equipment Identity) number - essential in case your device is stolen and you want to block the thief from accessing your network
*#*#7594#*#* -Make Power button turn off your device without displaying menu
*#*#4636#*#* - Display information about phone, battery, usage and WiFi
*#*#7780#*#* - Factory reset (deletes app data and apps, not firmware)
*2767*3855# - Complete phone wipe, including firmware (not to be used lightly!)
*#*#273283*255*663282*#*#* - Back up all your photos and videos
*#*#1472365#*#* - Test your GPS
*#*#1234#*#* - Display phone firmware and PDA info
You can access the above screen on most Android devices by entering *#*#4636#*#* on the dialpad.
*#*#232338#*#* - Show WiFi Mac address
*#*#8255#*#* - Access GTalk Service Monitor
*#*#36245#*#* - Access Email debug info Email
*#*#225#*#* - Events calendar
*#*#426#*#* - Debug info for Google Play Service
*#*#759#*#* - Access Google Partner Setup
#Samsung SECRET Codes :-
*#*#34971539#*#* - Show all camera information
*#*#197328640#*#* - Enable test mode for services
*#*#232339#*#* - Wireless LAN test
*#*#1575#*#* - Test your GPS (alternative to generic Android GPS test)
*#*#0*#*#* - Test your LCD display
*#*#4986*2650468#*#* - Display crucial phone information (PDA, Hardware, firmware etc.)
##778 (followed by the Call button) - EPST menu
#HTC SECRET Codes New :-
*#*#3424#*#* - HTC function test Program
*#*# - HTC Info menu
*#*#8255#*#* - Launch GTalk Service Monitor
##3424# - Diagnostic mode
##3282# - EPST menu
##8626337# - VOCODER
##33284# - Field trial menu
##786# - Reverse Logistics Support
##7738# - Protocol Revision
The function test menu on HTC phones can be accessed by typing ##3282# on the dialpad
