I have a diagram I'd like to reproduce in TikZ:
Picture a can (cylinder of radius r and height L) that has liquid in it. In each diagram, the can is tilted so that the surface of the liquid just touches where the top meets the sides. In the first diagram, the liquid covers the entire bottom, while in the second, only half.
Edit: Yes, I could do this myself given the time, but I'd like to see how others would handle the 3D aspect. Is there a better way to draw a projected circle than to draw an ellipse? [There you go @Andrew.]
The optimal code would use styles and named coordinates so that one could alter the diagram by changing only a few parameters.