The "Son Of A ***** (Gun)" Tool.
Any handy tool that you grab and throw across the shop while yelling, "Son Of A ***** (Gun)" at the top of your lungs after injuring yourself or damaging whatever it is that you are working on. It will usually bounce off a wall and end up in a place that is very inaccessible and will also usually be the next tool that you need.
A handy guide to help you select the correct tool for a particular job.
And finally, a tool I find myself using quite frequently!