I do most types of photography, I do street, portraits, general night photography, architecture, documentary, some other stuff occasionally, and I also do some video.
For just about everything BUT street photography, you need a tripod some if not all of the time. You can even do street photography with a tripod (I did some street work in Argentina with my 5x7, but that's another story altogether). Plus, it is the universal accessory - it will work with virtually any camera you'll ever own, from digital point-n-shoot to large format to video/cine.