A simple, stateless password manager.
In general, it is unwise to reuse passwords. Hashpass generates a different password for every service you use, so your password for one service cannot be used to gain access to any of your accounts on other services. Hashpass is unique in that it doesn't store any passwords; it simply computes a well-known hash function every time you use it. If your computer is compromised, Hashpass leaves nothing to be stolen.