Melky Cabrera has been in the league since 2005, but this came out of nowhere. In 2010, he had over 500 PA, and hit .255 with only 4 HR and 7 SB. He signed a one year contract with the Royals and ended up had an excellent season. He was traded to the Giants for Jonathan Sanchez a few months ago.
The Giants contended last year (86 wins and 4 GB in Wild Card race) despite coming in 29th in runs, so Cabrera could play a big role in the NL West if he can continue to produce like this. This is a contract year for Cabrera, and it could be a chance to go back to the playoffs (where he has mostly struggled, except for the 2009 ALCS).
Every other player on that list produced well beyond one season, but it's too early to say if this is something we can expect from Melky every year. He'll have his chance to show it wasn't a fluke in 2012.