*#06# for checking the IMEI (International Mobile Equipment Identity).
*#7780# reset to factory settings.
*#67705646# This will clear the LCD display (operator logo).
*#0000# To view software version.
*#2820# Bluetooth device address.
*#746025625# Sim clock allowed status.
*#62209526# - Display the MAC address of the WLAN adapter. This is available only in the newer devices that support WLAN
#pw+1234567890+1# Shows if sim have restrictions.

*#92702689# - takes you to a secret menu where you may find some of the information below:
1. Displays Serial Number.
2. Displays the Month and Year of Manufacture
3. Displays (if there) the date where the phone was purchased (MMYY)
4. Displays the date of the last repair - if found (0000)
5. Shows life timer of phone (time passes since last start)

*#3370# - Enhanced Full Rate Codec (EFR) activation. Increase signal strength, better signal reception. It also help if u want to use GPRS and the service is not responding or too slow. Phone battery will drain faster though.
*#3370* - (EFR) deactivation. Phone will automatically restart. Increase battery life by 30% because phone receives less signal from network.
*#4720# - Half Rate Codec activation.
*#4720* - Half Rate Codec deactivation. The phone will automatically restart

If you forgot wallet code for Nokia S60 phone, use this code reset: *#7370925538#
Note, your data in the wallet will be erased. Phone will ask you the lock code. Default lock code is: 12345

Press *#3925538# to delete the contents and code of wallet.

Unlock service provider: Insert sim, turn phone on and press vol up-arrow keys) for 3 seconds, should say pin code. Press C, then press * message should flash, press * again and 04*pin*pin*pin#

*#7328748263373738# resets security code.
Default security code is 12345