Here are a few lines of TypoScript code that really took me a long time to get to.

In TYPO3 4.x, I would fetch an image which is inserted on a certain page as a normal content element (CE) and use it for example as an site wide header image.
In this example, the image in question is located in the backend column 'left' (id 1) on the root page of the site, the PID of that page is stored in a TS-variable {$home_dir}, since I change it further down the page tree via TS-constants.
TYPO3 4.x
temp.headerimg < styles.content.getLeft
temp.headerimg {
...