Most interesting hacks require root and other tweaks, but here is a simple way of getting info on your device and changing some settings not possible in the normal menus. Simply open the dialer on your phone and enter some numbers!
Basic phone info
In the dialer enter *#*#4636#*#* You will then see a testing page, which gives you info on the phone, as well as battery stats and app usage stats. In the Wifi menu you can get info on the network you are connected to and more.
Change the power button action
Entering *#*#7594#*#* will bring up the menu to adjust the power button action. Dependent on your ROM you usually see a list of actions such as ‘Reboot – Airplane Mode’ etc, this allows you to remove these.
HTC Update checking
*#*# 2432546#*#* If you use an HTC device, you can force a check for updates using this code. This will bring up a notification telling you whether or not it has been successful. Be careful if you are using a custom ROM , as some updates may not be compatible with it.