Kannon, the Goddess of Mercy, can be seen as both a male or female statue. She is a Bodhisattva, which means she has reached Enlightenment but has postponed Nirvana (eternal enlightenment) in order to help others. She can be depicted with 1000 arms (that's the number they're going for, usually the statues won't have so many though) holding 1000 different things to be able to help people. Sometimes she will also be seen with 11 faces and/or a lotus flower.
Because I really love Kannon, Sanjusangendo was a must-see for me. It may be boring if you don't know about Kannon, but this is the kind of place that improves the more you know about it.