Now he's not necessarily the villain in the typical sense. He's not out to destroy or rule the world. But he is wondering around playing pranks on people that results in their deaths and disappearances. And he's always ready to mess around with the Winchesters. He's a troll and takes revenge in his own creative and humorous ways.
Originally the Archangel Gabriel, he fled Heaven because he was tired of seeing all the fighting in heaven between his brothers. He assumed the identity of a trickster and walks around Earth playing pranks on people. He refuses to help out and do what he can to try and stop the battle, hoping that he can force Sam and Dean into allowing Michael and Lucifer to use them as vessels for battle. He doesn't seem to care at the time that if the brothers say yes the world could suffer.
I love him as a villain because of his humour. He always stays in the background working by himself and messing around with people in small yet threatening ways. Just when Sam and Dean think they've stopped him he's lurking in the background chuckling away and skipping off into the sunset. He swallows enough pride to not boast about their failure in their face because at the end of the day he's looking to survive and doesn't want them hunting him down. Unless he just happens to come across them again and he can't resist playing tricks on them. Take season 3 of Supernatural. The brothers come into town to find a missing person and Gabriel gives Sam his own Groundhog Day experience as he witnesses Dean die a million and one times in bizarre and cartoon-like ways.
He doesn't want to end the world and go crazy with armies and have an obsessive need to kill the ones who can stop him. Villains like that always let their rage and ambitions get to their head and end up dead. Gabriel's just out to have fun and bring people down a notch. A villain who likes to teach people a lesson.
Seriously, how can you not love a baddie who torments his victims by doing this to them?
In season 5 Gabriel sends Sam and Dean into TV land where they have to be part of different programmes. In the video above Gabriel has moved them into a herpes commercial and poor Sam has to be the one who pretends he has it.
Now that's a trolling villain.