Mobile Secret Codes you must know at all times

For Different task there are different secret codes in mobile phone such as to see the IMEI number, Factory reset, Hard reset etc.

*#92702689# : To See life timer of mobile phone
*#06# : To See IMEI number
*#0000# : To See Software name and version
*#7780# : For Factory setting in Nokia mobile
*2767*3855# : To Format Samsung GSM OLD model
*2767*7377# : To Format Samsung GSM
*#7370# :To Format Nokia Phone
*#800# : To Know China mobile software version
*#0044# : To Know China mobile English Language setting
*#001# : To China mobile English Language setting
*#369# : To Change LCD contrast in China mobile

Add more if you noticed that some aren't listed through the comments box..