What would you consider to be the best and worst examples of the super hero team headquarters?
Personally I think that the best team headquarters is the fairly recent Justice League paring of the Hall of Justice and the Watchtower. The Hall of Justice serves as the public facade of the League housing meeting rooms, museum, and trophy room while the Watchtower is the place where the real work is done. It helps that the space based headquarters is out f reach of most villains, thus forcing them to focus most of their hostility on a ground based structure that serves as little more than a PR tool. The other thing that I appreciate about the Hall is that even though its a public place in a major city, it is never shown to be close to any other structure. Its usually sitting by itself in a park thus minimizing the risk to the surrounding city should it be attacked. (though the Metrotower on JLU, despite having ample parkland, was uncomfortably close to the other buildings in Metropolis). Asthetically I prefer the Young Justice Hall of Justice and the JLU/pre New 52 Watchtower III.
The worst headquarters, to me at least, are the crazy public skyscrapers that the Avengers and Fantastic 4 tend to use. They just seem reckless. They are everything that the Hall of Justice and Watchtower combo are not...they are insanely public targets that also manage to put the public at risk. The Baxter Building/Four Freedoms Plaza actually had tenants that frequently complained about all the destruction/difficulties caused by haing the FF in the buildings. Similarly, why would anyone agree to go to work in Stark/Avengers Tower?