I wrote my own password manager about a year ago, in java. It uses Vigenère encryption using a key the computer doesn't remember (that you have to write down somewhere). I still don't actually use it in my daily life, firefoxes password manager is pretty convenient and I'm pretty lazy...
By the way (you're quicker than duckduckgoing) Are you able to view and export password in plain text if you want to discontinue using the firefox password manager?
I've resisted using password managers up to this point, but it's getting to be a pain