Ask HN: Your favorite startup(s)?

Which startups are you closely following or are inspired by and why?

For me it's Watsi because of what they are doing in healthcare in such a transparent way. An excerpt from their About page:

While serving in the Peace Corps in Central America, a woman boarded a bus Chase was on and asked for donations to pay for her son's healthcare. She inspired him to start Watsi, and name it after the town he was traveling through at the time.