Be prepared- windy, cold & walking!
I liked the Golden Gate bridge, because, of course, it is one of the most famous bridges in the world, and I can say that I walked all the way across it. Just a warning- I went in July, and it was still really chilly- bring a jacket! Also, if you plan to walk all the way across, it was very hard to find a cab or shuttle for the reverse trip, so be prepared to walk in both directions!