Only with my evil characters, and I don't kill someone right off the bat. I try to be more subtle, at least initially.
There's a fine line between madness and evil.

Personally, no, I wouldn't and won't. I mean, I might talk to the person first, and if it happens to be a complete [censored] and a certain race my character is not fond of, I might just give him a beating, or worse. Eventually, but I doubt it.
I think a real fight would be a more entertaining "first kill experience" than praying on the weak(assuming it's not a guard...).