Traffic

Being stuck in traffic can be as fun as a kick in the 'nads, so it's a prime place to unwittingly get lost in your own thoughts, at least while the car in front of you moves.

We've all made up things with plates, composed entire songs that never made it any further, killed motorcyclists in our heads (If you live in Caracas at least), written entire books in our heads or attempted to profile other drivers by detailing their cars.

Might elaborate on this, but not in this post :D