On the second day of selection, I was chatting with a fellow juror who happen to be a law enforcement officer.
He told me that before the end of the day we would both be off the jury (I am a middle school teacher).
He was right by the end of selection every teacher, law enforcement officer and women with children were taken off the jury by the defense.
As a side note, I read later the guy was found not guilty.
You can add retired military to that list. We will never serve jury duty on a felony or capital case. Looking at the jury profile, it is about as brain dead as you can get:
http://blogs.discovery.com/criminal_report/2011/05/casey-anthony-trial-juror-profiles.html
You can also add security personnel. In my couple of years working as a Security Officer, I got in the pool three times and never picked. The last time I was in the courtroom and watched as the defense attorney took note of my name as I stood, waited to hear my occupation, and marked me off with a Sharpie.