I am going to say a corded or cordless drill with both driver and drill bits. You can't live without a good drill!
The most useful tool would have to be diamond pickaxe.
bow and arrow
microscope.
The Versatile Benchtop Table Saw is the most versatile power tool
It is a company which provide a useful tool and can be understand with the power of the development and in accordance with circumstances and so be useful.
Perhaps the most useful tool in tracking tornadoes is Doppler radar.
A healthy living human brain.
a shovel
when is the estimation of product is a useful tool
Control Charts
the too that is most useful in word is the print because it allows you to print out what ever you want....
A useful tool would be a spatula.