I particularly like the one built around a generic 2x20 text LCD.
Now that it's easy to make plates with a full-color printing process that doesn't need stamping, some states have gone totally overboard. In Texas, you can get a custom plate with the logo of most major colleges and NFL teams (even ones up in the "damnyankee" northeast states). You can even get plates with a sequential number on your choice of multiple alternate backgrounds, such as white letters on a pink background, but most of those are "for a cause" art.
And while they require you to change plates after a number of years (due to limited lifetime of the reflective material), I still have and see many of the old stamped plates. Also it seems that at some point they started requiring a new license plate when a vehicle is sold, which only increases the churn.
Of course when you get a new plate, it is a new number, that way they can just have a stack of new plates in the tax office. Back in the day, Oklahoma used to re-issue you a fresh plate with the same number every year with a prefix based on your county (like a telephone number), until a fire broke out in the state prison (probably from a riot) and destroyed the equipment. Then they finally accepted that, duh, plates can easily last ten years.
I think Virginia is another state infamous for plates gone wild. This one is my favorite.
I saw a Rolls Royce with plate "BR 2" - my initials
Your last name starts with a digit? Pleased to meet you, Mister 2! (But who is Number One?)
All life evolves by the differential survival of replicating entities. -- Dawkins