In the first episode of Season 4 (Lazarus Rising), we meet Castiel, who is in fact an angel. When Castiel proceeds to knock out Bobby, wanting to talk to Dean in private, some chanting can be heard in the background. The chanting begins as Castiel puts two fingers to Bobby's forehead, inferring that this is how he puts him to sleep.
Now, I'm assuming this chanting has some divine background, relating to God or Angels, but my main point comes in Episode 20 of Season 1 (Dead Man's Blood). Similar (or maybe the same) chanting can be heard when John fires the first colt bullet at the lead vampire.
Seeing as how this chanting can be heard both times (although it is never heard again when the remaining bullets are fired), and that one of those times has very close connections to an angel, this raised some questions in my mind about the history of the colt.
Perhaps the colt made by Samuel Colt is a holy weapon, or perhaps that Samuel colt himself was an angel? Im just throwing random ideas out there, but as far as we know, the colt can only kill supernatural beings and has the same properties as Ruby's knife, which failed to kill Castiel. Maybe the knife is somehow connected to the colt as well, who knows? Post your random ideas as well! O_o