What is your favorite statistical graph? This is a favorite of mine

This example is in a humorous vein (credit goes to a former professor of mine, Steven Gortmaker), but I am also interested in graphs that you feel beautifully capture and communicate a statistical insight or method, along with your ideas about same.
One entry per answer. Of course, this question is along the same line as What is your favorite "data analysis" cartoon?
Kindly provide proper credit/citations with any images you provide.
 A: I think that Anscombe's quartet deserves a place here as an example and reminder to always plot your data because datasets with the same numeric summaries can have very different relationships:

Anscombe, Francis J. (1973) Graphs in statistical analysis.
American Statistician, 27, 17-21.
A: I like very much your examples!, but one shocking and simple graph for my point of view is that one:
propaganda nazi

A: I always enjoy reading this Sankey diagram (a type of flow map) on the French invasion of Russia by Charles Joseph Minard in 1812:

Charles Joseph Minard's famous graph showing the decreasing size of
  the Grande Armée as it marches to Moscow (brown line, from left to
  right) and back (black line, from right to left) with the size of the
  army equal to the width of the line. Temperature is plotted on the
  lower graph for the return journey (multiply Réaumur temperatures by
  1¼ to get Celsius, e.g. −30 °R = −37.5 °C).


(click on image to zoom)

In 2nd position, this 3D pie makes me laugh each time I see it:

It is the perfect example of how misleading a 3D visualization can be: Steve Jobs clearly used a 3D pie chart to make Apple's market share look much larger than it was:

The 19.5% market share slice for Apple's iPhone somehow looks bigger
  than the 21.2% market share for the mish-mash of "Other" brands.

Same Steve Jobs 3D trick on another slide:

A: I hope not to push things here too far toward the humorous side with an early response that's in that vein (+1 for @GregSnow's theoretical answer!), but since I already have an entry in the favorite cartoons thread, I'll add a graph here.




By Jorge Cham of Piled Higher and Deeper infamy, as per the © on on the bottom right margin that I hope I'm respecting! I particularly like the existential crisis bump, because I'm an existential psychologist with interests in motivation and emotion. As such, it's my (un)professional opinion that this is pretty accurate! $\mathbf{\large ☺}$
A: Another famous visualization of data (we can have a semantic argument about whether it should be called a graph) is John Snow's 1854 map of cholera cases in London:   

A: Thinking in terms of a figure that packs a lot of information, I like this one:  

It comes from the main page of the R Project for Statistical Computing.  It won the R homepage graphics competition to be so displayed.  The R code to produce it can be found by clicking on the figure on the R homepage.  
