[El Gato]

I also like the concept of bringing 20,000 pounds in from orbit.

That would be city buster, not a bunker buster. A small compact city or town at least. Sort of like one of the boroughs of New York, area wise.

[SampleMan]

Let's not bicker about who killed whom.

My calculation show a relative energy release equal to 145,100 lbs. of TNT. Comparable to a very small nuke of less than 1 kiloton. I believe Fat Boy was 5 kilotons.

However, as a penetrator, the surrounding area on the surface would not be so radically impacted. I will give you a good sized crater.

Of course, there would be no need for explosives.