I can't think with a single voice, a fact that irritates me greatly. Every time I try to ponder something, every time I try to concentrate, my mind is split between a multitude of different voices, all of which belong to me, but, at the same time, feel rather out of my control. It's hard for me to tell if I've generated any of the thoughts I think, because many seem to come from nowhere.
When I try to figure out problems, I typically have a neutral voice arguing the point of view that I consciously prefer - this, I would have to identify as being "me", albeit in a very basic sense. Aside from that single voice, my unconscious mind selects for me one or two other people, who generally relevant to whatever is being debated. For example, if it's something related to human behavior or psychology, I might be ranting on and on to a psychologist I had to visit when I was younger, with him occasionally butting in to point out a contradiction or inconsistency. If I'm dissecting the state-of-mind of a friend, I'll either be talking to them or an entity I'll christen "The Invisible Man" - I don't have a visual identifier for this being, all I know is that I'm not consciously producing the arguments and thoughts it brings to light. This "voice" is the most helpful, because it feels more like I'm talking with myself.
The only across-the-board similarity is that the other conversational player, not counting "me", is always cast in the role of devil's advocate.
Normally I keep these conversations in my head, but I really do like to vocalize them. I've been considering buying a broken Bluetooth headset, for the sole purpose of being able to mull things over with myself in public without looking like a total lunatic.
Eh, it's entertaining, I guess. Sometimes I'll find myself swearing at myself, other times I'll be frustrated with the stupidity of a person that seems separate from "me", but really is me. Occasionally, I'll become aware of the sheer incongruity and insanity of these thought processes, saying to myself, "You know, this has all got to stop. I am sick of you acting this way!"
Then I'll realize that I'm not referring to myself in first person, laugh a little, and shrug it off.