Personally, I think one important event in history was when Rosa Parks refused to get out of the back seat of the bus. Obviously, this is thread will be opinionated, so let me know what you think are important events!

Ahh, this is going to be a rough ride. There are too many important events to specify the most important xD

Anyway, I must agree with you about Rosa Parks. I actually do not think it is the most important, but rather it is a stepping stone that furthers the cause for African-American freedom, or rather racial freedom in the United States. 

Christoper Columbus reaching the West, introducing the New World. Europe starts to come over and populate. That surely is important. 

Newton and his universal law of gravity is very much so important, for it does help shape science theories and laws to this very day. I wouldn't call this an event of sort, but it is very important. 

These are just a few examples, but there are way too many important events and discoveries that helped change and shape the world that we currently live in.

I would share the place with the invention of the fire and wheel  and taming of the dog and the horse. I would not be typing this without one or all of these.

Brigand : All these are excellent.

The creation of written and verbal communication and shared language.
The domestication of animals and plants
The control of fire
The creation of the wheel
The discover of germs and bacteria
The creation of trade and money representing value
The discovery of math and physics

The list can go on and on.

You can even go Big Picture and say the asteroid that killed the dinosaurs hitting the earth to allow mammals to become the dominant land animals.  Otherwise, we'd be reptiles typing away at keyboards here.

This is a pretty good thread for various ideas. For me I would pick the entirety of World War 2. Why do I pick a war? Well..the sad but true nature behind war is the victor gets to write history. I like to think myself as a bit of a WWII buff because I had family involved with it, but despite how bloody this war became it brought with it many inventions, many jobs, and so on and so forth. But one of the biggest things about wars throughout history comes down to the basic questions of "what if?".

Without having this war go the way it did the entire world would be completely different. The United States and the rest of the world could be a totally different country or even have become a part of another country. America could possibly no longer have rights or the freedom many of us take for granted. We may not have the technology we have now because our Space Race against the Soviet Union would've never happened. 

Any and all wars do sadly take a big part of history despite the depressing state that comes from it but if you look past that, it is another way to see how we as a species, as cultural human beings made mistakes. It leads us towards a path that could help prevent such bloody skirmishes to break out across the world so long as we pay attention to history and find way to fix things now and in the future rather than ignoring them.

The arrival of glover in japan.
He sent Japanese citizens illegally to the uk to study, who later became japans rulers.
He convinced the British to support the pro modernisation Japanese rebels. He equipped and trained in the British style, the Japanese army.
He brought industrialisation to japan.
This caused japan to conquer much of Asia, bring america into ww2, cause lasting regional hostilities, the collapse of Europe's Asian empires, potentially the route to communism for china and russia since the wars japan fought with them caused great domestic problems for those countries, established japan as the richest most western Asian country, so on and so forth.
Arguably the man caused many problems for the world but the japanese idolise him, they have statues and everything. I suppose they got the better end of the deal.
I have to wonder what the world would be like if it hadnt happened. Especially given how important japan is in modern research and creations.

The birth of Mohammad.
The birth of Jesus.

So many people have died in the name of religion that it has definitely altered the course of history. Think about it, every time that someone's life is cut short by being murdered, their potential to advance human civilization is finished. Also, any of the potential contributions of their unconvinced offspring and their descendants is also lost. There may also have been offspring and descendants who never lived that would have done horrible things or invented un-imagined weapons of destruction. 

Something can also be said about Jesus and Mohammad's positive effects on world history. (I'm not entirely sure what they are, but I'm sure it can be said.)

I'd say the most important "event" in history was something that didn't happen that could have easily happened. About 70,000 years ago a Supervolcano Toba erupted, which caused a nearly world-wide ecological disaster and the human population dwindled to about 5,000 people. This population of humans could have easily died out from a number of things like famine or disease like so many other species have died over the course of the Earth's history, but didn't. Human history could have ended a long time ago.