Units sold: 150 million

As a standalone phone, the Nokia 1110 has everything a user needs. It's small, clean and compact, and comes equipped with a durable battery. And it was for this simplicity and convenience that, when it debuted in 2005, the Nokia sold like mad. In a run preceding Nokia's 5230 smartphone, the 1110 model sold about 150 million units across the world, many to first-time cell phone users in developing and underdeveloped countries. In many nations, the prepaid phone retailed for just $90.

* Bing: What cell phones costs less than $100?