Here are fifteen handy photoshop shortcut commands. They are handy in many occasions because you often have to move your mouse cursor in order to select a tool, but this means moving it from a position that may be difficult to find again. Plus, it becomes a very long process if you have to keep switching tools very often. The buttons are all shortcuts, and some of them work on web browsers too, such as Ctrl + Z and Ctrl + 0.
Helpful and handy is right. Knowing simply what keys to press in accordance can ease the pain and trouble.