What's your suggestion on solutions that blossom with OOP?

Quoting a post on another site:

"I've seen a lot of terrible C++ code and it's not just from people who don't understand the concepts. I've seen a lot of coders who know exactly what an object is and can explain polymorphism and all those technical OOP terms perfectly. But if they don't know when to use it, they'll never be able to take full advantage of it. I know because I was like this myself. I had read a book on OOP in high school which explained all the concepts, but I went years before I actually used them because I didn't see when they'd actually benefit my code."

What suggestions would you make for any projects or problems that can be tackled solo (for practice) that are just smarter to do with OOP?