Actually I'll just go ahead and put mine up now.
My choices:
1) DISTANCE: You can have perfect technique, speed, and timing, but if you aren't in the right place to hit, you'll never hit the guy. This also plays a part in grappling for many moves, though the ranges are more subtle and precise.
2) TIMING: I put timing ahead of technique because you can have great technique and bad timing and still not get the hit, as well as put yourself in a BAD position. But if you are the right distance, and your timing is good, you can knock a guy out even with a sloppy punch. More than a few black belts have been knocked out by street fighters that had bad technique.
3) TECHNIQUE: Even if you do knock the guy out with a sloppy punch, what becomes of your hand. There are more than a few movie punches where one guy punches out another guy, then either breaks his hand. or has to shake it off. I ranked technique higher than speed becuase if you knock a guy out with a very fast punch and poor technique, you can mess up your hand all the more.
4) SPEED: If the other three things are in place, speed can only help you. If any of the other three are not there, speed can actually put you at a disadvantage.
Now, to be certain, I left things out. I left out targets, relative position, and power, etc. This was more of a discussion starter. Plus, in my oppionion, relative position falls under distance, targets fall under technique, and power is mass times velolicity, so it falls under speed and technique anyway.