The most useful object in the world is a screw. not kidding
The most appropriate and most common exercise machine for home use is treadmill.
the world's most amazing machine may be the human body itself
50 cal. machine gun. i don't know who decided to use it.
What the most useful machine is, is a matter of opinion. Some would argue that the wheel is the most useful machine, and others would argue that the lever is the most useful.
Most of the parties involved already had machine guns in their inventory prior to the outbreak of the First World War.
The use of a commercial coffee machine is to make coffee fast in the morning. Most people need coffee to function in the mornings. That is the use of commercial coffee.
The machine gun was introduced along with the use of airplanes.
They were a powerfull defensive weapon.
The 30.cal machine gun.
The LeaveMeAloneBox is the worlds most useless machine. It's sole purpose is to turn itself off after you turn it on.See the related link.
mori seiki
Tanks and machine guns.