Fortunate events that happen to the less fortunate or to individuals who are not expected to succeed (i.e. success of mentally and/or physically challenged individuals). Also, superficial successes the come to humble individuals who realize that being a person of high moral character is much more important than gains of a superficial nature.
You would think that Billy, the blind kid from 4C, would have some Gump luck, but I guess not. He bought a bird whose head had fallen off, but was taped back on by Lloyd, the sick limo driver.