Stephen Jay Gould once noted that The Far Side by Gary Larson adorns more scientists’ office doors than any other series of cartoons. This was certainly true a number of years ago, but I think that honour may have passed to a new generation. In particular, Piled Higher and Deeper by Jorge Cham (PhD) is now to be found not only on faculty doors but on a large percentage of graduate student office doors as well. (I even bought copies of the books to keep in my lab).
Here are some of my personal favourites: