The Tokyo Subway Ticket gives you unlimited rides on all Tokyo Metro and Toei Subway lines in Tokyo. If you are traveling around Tokyo, these tickets can be quite a good deal and give you a piece of mind in terms of your transport costs. The combined network of Tokyo Metro and Toei Subway also allows you to get to almost every major destination within central Tokyo.
This is the recommended pass for any visitor to central Tokyo. Note that this pass does not cover routes to Narita Airport, Haneda Airport, Odaiba, and Tokyo suburbs, all of which are outside of central Tokyo.