All of the suggestions thus far are really great. I would also consider Einstein's theory of General Relativity, which was a staggering achievement...
..if we want to talk about the things that really changed the world and made us into the creatures we are today, I would offer the following as being the most fundamental:
-- The mastery of fire and the use of it to cook food and keep us warm
-- The invention of the fish-hook, especially the version with the barb (some of the earliest recorded fish hooks were from Palestine about 7000 BC)
-- The invention of stone blades (knives, axes, and spear heads)
-- The invention of the bow and arrow
-- I don't know if I would class spoken language as an "invention" -- but certainly written language has to count.
-- MUSIC!!! From multiple people banging on things together to whistles and flutes to stringed instruments and song.
-- ART!!! Whenever I see pictures of stone-age cave paintings and Australian Aboriginal paintings I am rendered speechless (and it's not often you'll hear that).
-- BEER!!! I can't help it. Alcohol in general, and beer in particular, certainly makes me happier and my life better (check out by recent blog http://bit.ly/ns2XHe)
The above suggestions are just off the top of my head -- I could waffle on for hours about this (or most things, come to think about it)
Thank goodness it's Friday :-)