the Barbican centre - superb inside & out. I also have a soft spot the South Bank / National theatre thing. There are of course some truly horrible brutalist buildings, bit also some that are rather good. A regular failing was to make the buildings very hostile-seeming at street level,l. Not unique to brutalism but certainly a strong tendency - and arguably this well intentioned segregation of people from roads / cars made the people bit more hostile & lonely
PS for both converts and unconvinced I recomend the book Brutalism & and one simply titled "concrete"