Samsung Android Secret Code
*#*#4636#*#* - Phone Information
*2767*3855# - Hard Reset
*#*#7780#*#* - Factory Reset
*#*#7594#*#* - Change End Call/Power Option
*#*#197328640#*#* - Service Mode
*#*#273283*255*663282*#*#* - File Copy Screen (Backup Media Files)
*#*#526#*#* - WLAN Test
*#*#232338#*#* - Shows WiFi MAC address
*#*#1472365#*#* ou *#*#3214789650#*#*  - GPS Test
*#*#1575#*#* - Another GPS test
*#*#232331#*#* - Bluetooth test
*#*#232337#*# - Shows Bluetooth device address
*#*#8255#*#* - GTalk Service Monitor

Codes to launch various Factory Tests:

*#*#0283#*#* - Packet Loopback
*#*#0*#*#* - LCD test
*#*#0673#*#* - Melody test
*#*#0842#*#* - Device test (Vibration test and BackLight test)
*#*#2663#*#* - Touch screen version
*#*#2664#*#* - Touch screen test
*#*#0588#*#* - Proximity sensor test
*#*#3264#*#* - RAM version

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