Is a tail gun necessary on a B52?

No, at least in my opinion. If you ever get a bandit close enough to your jet
to use a 20mm cannon, many things have gone wrong from the OCA push to the
AWACS coverage.

Has one ever been used as a defensive
measure in recent times?

This is debateable. According to several books and official Air Force history,
yes it was used successfully twice during Linebacker II. According to a few
books, including the latest; "11 Days of Christmas", the two supposed
shootdowns were probably F-4s diving away from BUFF friendly fire. Our own Ed
Rasimus who shared those same skys that December doubts they were real kills as
well.

Also, refresh my memory, it was a B52 that Slim Pickens was dropped from
in the movie ( as per BUFDRVR's signature )??

Sure was....yaaahoooo...

And as more of a side note, was BUFDRVR's H
model built before or after the movie came out?

Before. The movie was made in early 1963 and released over Christmas 1963.
There's a scene in the movie where our hero, Slim Pickins, is reading the
contents of the survival kit and says; "shoot a fella could have a good time in
Vegas with stuff". If you watch closely, the word "Vegas" is dubbed in and Slim
actually says "Dallas". This was changed prior to the movies release due to the
shooting of JFK in Dallas in November '63.


BUFDRVR

"Stay on the bomb run boys, I'm gonna get those bomb doors open if it harelips
everyone on Bear Creek"