This little guy, more formally known as Theridion grallator, is native to the Hawaiian islands. It grows to a length of about five millimeters. On The Island of Maui, the patterns tend to be hereditary, but on the other islands they appear to change based on the spider's diet. Given their small size, as well as their ability at hiding during the day, they aren't a major prey item on anyone's menu. The purpose of their coloring is still unknown.
Picture posted on Wikipedia commons by user Kahlzun