A Normal Quantile-Quantile chart. This reveals departures from the normality assumption. Where the residuals are normally distributed, the points on the line will form an approximately straight line running from the bottom-left to the top-right. Shapes other than a straight line indicate that the normality assumption may not have been satisfied. See this answer on Cross Validated for more information.

For example:

## Acknowledgements

Uses `plot.lm` and/or `plot.glm` function from the `stats` `R` package.