Team Free Will
Dean: This is it.
Sam: This is what?Dean: Team Free Will. One ex-blood junkie, one dropout with 6 bucks to his name, and Mr. Comatose over there. Awesome.
After Dean sarcastically named himself, Sam and Castiel as "Team Free Will", it was quickly picked up through fandom as shorthand for referring to their alliance in stopping the Apocalypse. It could also include Bobby.
Castiel: And of course, I remember the most remarkable event. Remarkable because it never came to pass. It was averted by two boys, an old drunk, and a fallen angel.
"Team Free Will" is also used sometimes to describe fanfics which feature Dean, Sam and Castiel in a sexual relationship. See Dean/Sam/Castiel