Passgen

Passgen - unique password generator. Generates password based on (web) service name and master-password. Any inputted data or generated password doesn't be stored.

*** Disclaimer. ***
Password generation algorithm is based on whirlpool hashing and isn't suited for cryptographically secure key derivation.
Don't use this app for very important things, such as encryption passwords. The longer your master password is, the better.

That being said, it's still better than using the same password everywhere.

Passgen is open source project written using Qt Quick Controls 2. You could find source code here: https://github.com/zettdaymond/passgen