I have a soft spot for brutalism, especially neo-brutalism, especially something like the Bocconi University in Italy:
http://www.graftonarchitects.ie/work/projects/project.php?resource_id=225
I also like brutalist buildings that seem incongruously planted like the National Library surrounded by architecture that it doesn't fit in. It's kind of mischievous in retrospect. So I like the National Library. Someone here posted pictures of the Barbican Centre in London, which is one of the finest pieces of brutalism in the English-speaking world and now a listed building. It actually grows on you after a while.