Here's an obvious one that in my recent experience is worth mentioning.

The plastic pencil/coin tray just behind the shifter and under the sliding retractable cover is removable and hidden below it are the two front cup holders! (... be nice if these were a bit bigger... but I can at least fit one large coffee thermos for my commute).

Believe it or not the previous owner had no idea and complained of no front cup holders (after owning and driving the car for 4 years).... said he would typically reach back to the passenger side cup holder for the rear seats in order not to dislocate his shoulder or crash getting to the driver side one.

Thanks to all for this thread. Keep it up.