To learn Go, I made a small app that supports encrypting files with a public key where the keypair is generated from a password. Because I want my backups to be encrypted but it offends me to keep symmetric keys lying around. With this you can just generate a file containing the public key, stream your file through the app, and decrypt it later with just the password. It's very minimum viable product, but I'm confident that the crypto is done well.

https://github.com/TomatoCo/warren

(It wasn't exactly over a weekend but it only had two or three days of effort put into it, which I think meets the spirit.)