Graphs and charts are a great way to add some visual interest to presentations and papers. They should also serve a purpose, of course, not simply adding eye candy. Every once in a while, I see a truly great graph or chart that demonstrates both aspects perfectly: visually appealing but also highly informative.
One great example is this graph shared by I Fucking Love Science (IFLScience for people put off by the F-word or, you know, if you're into that whole brevity thing):
Read more about it here.