Square<p>1) They solved a really hard problem. Basically they opened channels for merchants that used to only be able to take cash to credit cards. I have already used this twice on the consumer end. Once at a concert to buy a tshirt, once a cupcake food truck downtown.<p>2) They did an exceptional job of design in both hardware and software.<p>3) They had a real vision on their own, 'Apple Style' where they saw the problem and had a vision to a real solution. They didn't have to make a MVP and keep iterating (not that doing that is a bad idea) but have a vision that turns out to be true is always very impressive to me.<p>4) They executed in a exceptional time period. They had everything in place from from engineer to design and operation in the amount of time other startups take to make a webapp that is much less as sensitive (read: involves larges of amounts of money in a traditionally slow industry).
Of companies that are still in "startup mode" it's hard to say. Of recent (or semi-recent) startups that have achieved success, or some degree of success:<p>1. Tesla Motors - because they build sweet products and have a CEO who I admire.<p>2. Facebook - because they've made their founders a metric buttload of money, and have impacted millions (if not billions) of people around the world.<p>3. Scaled Composites - Because they're on the forefront of doing something amazing... making space-travel dramatically more practical and accessible.
Square, before anything else. I literally had a startup-gasm after the website was fully loaded.<p>After that, I'd say SpaceX, for making private-owned space travel a reality, and then Dropbox, for revolutionizing (in a way) the way we synchronize our files between devices.<p>The last two will (hopefully) be a basis for my future startup(s).