The California Capitol Building. I live in Sacramento, California, and the capital building is the most distinguished landmark here. We have a few others but that is probably the one that stands out the most.
I currently live in Singapore. The most distinguishing landmark and one of the newest too would have to be the Marina Bay Sands. It stands tall and you can see it from far. Its design is also unique and it has a SkyPark. See a picture of it here: http://hubpages.com/hub/Shopping-Singapore-Marina-Bay