In your opinion what is man's greatest invention?

Man's greatest invention is Airplane

Man's greatest invention is Telephone, imagine life without such communication tool.

The one of the most important invention of modern man is computer and internet. It seems that in modern world each and every small activity has to pass through these two things directly or indirectly and we can't imagine our world without it.

adisonhardy, you seem to be more descriptive thus making your point more appearing. Well, I'm Learning....

Man's greatest invention are medical equipment, do you know world population would have drastically reduced or even be close to wipe-out without all these equipment. 

Television and internet is greatest for me, because I love information.

Man's greatest invention is "Pen" simple but powerful tool.

Yes i agree with Christian, Pen is the most important invention which is used from ancient time in man's history in various formS. I think that today's all  technology invented just because of ancient invention such as "Fire" and "Wheel". Which was basic invention but we used them till today for inventing new something. So these all ancient inventions are more important.

Because invention started at something, not from the air. Pen is the one of such invention that looks little and simple but can do wonders, depends on who is holding it.

It is simple . After shave losion so addicted to it.

Man greatest invention is computer