When I first started coding, I followed a tutorial where I wrote a program that would display the 1998 Chicago Bulls starting lineup. That was in Python initially (that program is in the python folder as bulls.py. It's essentially the same as the one in the tutorial I followed). Since then, I've been using that program to help me learn new languages.
So far, I have Python, Rust, and C++. I'm looking to learn more languages and will be adding them as I learn.
As an aside, if you'd like to check out the same tutorial, visit likeiamfive.com. The instructor, Matt Blank, is a great guy and he's the main reason I'm a programmer now.