A game that I've seen referred to as 321 Word (or nowadays, Say The Same Thing) was certainly entertaining on car rides in my youth.

Here's a video of people playing it. https://www.youtube.com/watch?v=htdtUDepcok

The objective is that you both say a random word. Then both those words together make you think of a different word, and you keep going until you finally both come up with the same word. It goes on really wild tangents, so how you start has nothing to do with how it ends.