The kind of errors I hate the most are the ones you cannot even find in the documentation. When you get no compiler warnings, and even an incentive from your preferred auto-completion tool to go straight into them.
Todays such error is the following:
byte[] buffer = /* something that fills the buffer with the contents of a string*/;<br ...
@adurdin has made a skin for the iPhone simulator that may wear less on your eyes when you're sitting there developing all day: 