Hi Blue fire!
I believe that all scenarios would be rather disturbing.
And unfortunately, all these scenarios discussed here are possible.
Here is an interesting link that will let you calculate the effect of any type of impactor on the earth. Im not sure of the Algorithyms they used, or how accurate they are, but its results are quite interesting.
you choose the type of impactor, the speed and angle of trajectory, and where it strikes the earth, it will give you an idea of what could cause a 10 meter wide crater in a city, you might be surprised on how small the impactor could be to cause this scenario.
http://www.lpl.arizona.edu/impacteffects/
Dennis
PS; nice thread!