[x] Transportation

Communication comes in second.

boats.

I'd go for transportation, 100%.

all

transporation...

its also a form of communication... but lengthy

yeah

What about antibiotics or sanitation? Both saved innumerable lives.

The wheel is good I hear.

up

I voted Communication Devices, but not because I believe the most useful invention is a device, but because I believe it is language. The ability to communicate with each other has proven itself most useful.

watch donnie darko lately?

but seriously, antibiotics and sanitation really greatest invention ever...

id probably say cooling/heating devices next, then transportation, then the phone etc (but i would consider the computer a communication device as well)