I'm writing a lesson on debugging for my students. They will have already had a lesson on how to read code and do walkthroughs, either manually or using the debugger. They currently know about if, while, types, math operators, and have some experience with but no formal training in functions and methods. (We're finishing ch. 3 of Dawson's Python Programming for the Absolute Beginner).
So the lesson on debugging will emphasize verifying that the code does what it looks like it should do. In addition, we'll discuss common errors (bad indentation; naming a function instead of calling it; off-by-one; infinite loops; etc.).
So: what Python errors cause you fits? Or, do you have any hair-pulling stories to share? Or, do you have any "I had to debug someone else's code and it was a stupid ___ error" stories?