What are some essential apps that are easy to code?

I want to build my portfolio with a project that isn't purely for fun, something that provides good function, but I'm having programmersblock.

What are some apps that are essential for people, programs that solve everyday problems, regardless of whether it's for normies or programmers?
Additionally it'd be preferred if the app could be used in the terminal since GUI programming is complex in languages other than Python or HTML+CSS.

Thanks in advance.
Cheers!