I assume you have seen the Weekends Away from Tokyo thread. If not, there are daytrips listed there too. Like chuckd mentioned you won't be able to actually visit Mt.Fuji in the winter, but the Hakone hot spring area is worth a visit. Once you've been to Nikko it might not be necessary to go to Kamukura to visit yet more temples and shrines though. For such a short time in Tokyo, you'd be better off taking your time to explore the city without having to rush too much. You can shop and eat 'til you drop. I can spend hours at Tokyu Hands and exploring the food sections in the basement of the department stores. I also prefer the Omote-Sando/Harajuku shopping areas to Ginza/Nihombashi area.