Starcraft Universe: Chronicles of Fate is an upcoming mod for Starcraft II that pretty much blows everything else out of the water.
The game will feature a 'mix of Diablo, Starcraft and Warcraft' and is currently in Alpha testing.
Feast your eyes:
SCU looks to be the most sophisticated mod (custom map) to date for SC2.
The story goes something like this:
>January 2011 - a youtube is uploaded of a SC2 mod that appears to be using the game engine for WoW style play.
>The map looked so cool that, for fear of stand-alone business marketing, lawyers at Activision pulled down the video from youtube and began threatening legal action for 'copyright infringement'.
>However, Blizzard took a look and decided that not only was this really cool work, but they also asked the map maker, Ryan Winzen, down to Blizzard HQ to talk about the future of his map making.
Ryan Winzen and his crew now work as employees in Blizzard, with professional equipment and consulting. This is exactly the kind of creativity the community thrives off of~
(You can read more here: http://us.battle.net/sc2/en/forum/topic/1922563226?page=1)