I imagine that the only person I could probably push over the edge would be Himself, and he me. We adore each other, but you know that hate and love are not opposite sides of the same coin, but merely two stops on the continuum of strong emotion (indifference is the opposite side of the coin). 
Least likely to kill me? Probably my parents, or my little sister, who for some reason, adores and admires me and wants to spend time with me. 
me: So, who’s most and least likely to murder you?
Hamish: Most likely? My parents or [Evil Ex-Roommate.]
me: Fortunately, they’re all now safely ensconced in British Columbia.
Hamish: Walled off by the Rockies. Right, I planned it that way.
me: And least likely?
Hamish: I’d have to say you. Whether because of friendship or because you couldn’t get it together to murder anyone.
me: I could too!
Hamish: I know you, Matt. Admit it, it would take you longer than your lifespan to get through the stages working your way up from “strongly worded letter.”
Just to be a jerk. Also to justify your $200,000,000 annual salary.
Most likely would be my evil ex who sat around drinking beer all day while I worked and went to school. He complained that I wanted too much sex and I made him feel bad for being unemployed. Now that I am very sucessful in pretty much everything he works part time at the pizza place down the street and still lives at home with his father. Jealousy would probably be his motive.
Least likely to kill me would probably be my parents or my current roommate. They think I am super awesome.
The butler did it.
Regards,
Shodan
Most likely would be one of my flatmates. It’s been my turn to clean the bathroom for a while, but I haven’t gotten round to it. My excuse is that I’m too lazy. I think that’s a very good excuse, but for some reason not everybody agrees with me.
Least likely would be Sir Francis Drake. He’s been dead for several centuries, and even if he were alive he’d probably be on the wrong side of the world, and I doubt he’d be the slightest bit aware of my existence. Yep, I am pretty damn sure that Sir Francis Drake will not murder me.
Hmm. This gets tricky. Perhaps my husband or my MIL or my boss’ boss. (unfortunately, you did not ask whom I would like to kill–same answer. Heh. Just kidding, mods!)
But. (you knew there was a but, right?).
My MIL weighs about 90 lbs, and has shaky balance–she would have to poison me or use a gun (which she does not know how to do).
My husband wouldn’t because the kids would hate him for all time.
Who is most likely to kill me? I neither inspire great love or great hate, so I have to say I dunno. Perhaps the corporate equivalent of Darth Vader that I work with, but she would do it just for kicks.
Least likely would be my kids.
I’d just like to say cheers to Skald the Rhymer for posting the first ever spoiler box that I haven’t highlighted. That’s some powerful spoiler-fu.
So right now I’m the least likely person in the world to want to kill you.
Depending on my curiosity, that may change. Drastically.
Before my corpse was room temperature, the cops would have my ex locked up and her lawyer (paid for by moi) would be encouraging her to accept a plea agreement. Everyone else would come in such a distant second, that they would never be considered.
I don’t have any real enemies, which is fine with me. (There are people who don’t really like me, but I doubt they’d murder me.) There are a couple of people who fit into the second category.
Well, now that I think about it there is this girl–in reality a metatheric being from the Akashik plane–who blames and hates me for her incanation into this loathesome corporeal realm. However I have been assured by Kevvner the paradoxically unnameable that she is pledged to the Forgotten lords of Ise, and they have commanded her to respect my life and property.
Least likely to murder me? My wife.
Most likely to murder me? Also my wife.
Who the cops should look at first? My kids. Any or all of them.
My ex husband. Because I am employed and successful and happily married and all the way across the ocean with our son (with ex’s blessing, I didn’t kidnap the son) because ex couldn’t manage to raise the kid (as he wanted to do) and keep a job OR his new 19 year old wife for more than a year. Since ex is prone to psycho-drama meltdowns, I imagine if I was murdered, it would be in a fit of “woe is me, it’s all so NOT my fault” rage after he flew over here on his last dime to do it.
Lease likely, my current spouse, because…well, because. He wuvs me. 
Cheers,
G
If I turn up expectedly dead, a former Australian Competition and Consumer Commission Chairman Allan Fels should prove a person of interest to the police.
Least likely? Hmmm. Ex-Beatle George Harrison - 1) because he seems like such a nice fellow and 2) he’s busy being already dead himself.
mm
In order for there to be suspects, you’d have to notice I was gone.
Most definitely The Queen would be number one suspect.
For many years now she has known that I am the rightful heir to the throne and ultimately the world…the old bat just refuses to acknowledge my letters and phone calls.
It’s just a matter of time before the hit squad arrive at my front door
Hal Briston
Do I really need a reason?
You pissed off the ACCC? Go you!
Cheers,
G
Don’t worry…you’re only about fourth on my list…
Most likely? Hmm, I can’t think of anybody who would care that much. That crazy chick that doesn’t talk to me anymore probably.
Least likely? My boss?