There was a huge function that had to be split in no less than three separate files and then pulled in with #include directly into function body. These were #included in multiple other places, for greater obfuscation effect.

I opened another file (this time .NET), still same application, though... I jumped with my editor into middle of roughly 25k LoC of code... to be faced with empty screen. A bit surprised, I started dragging the scroll bar and then suddenly the code started showing on the right side of the screen... There was a span of roughly 15k LoC that was indented so much it was off the screen.