Possible Duplicate:
Cunning (La)TeX tricks
Here, by hack I mean a short, elegant, or even counterintuitive definition/macro etc. that solves a task, often in a surprising way.
Background
Many languages/systems collect those lists of hacks, as there are a fun way to learn some of the intricacies of that language/system. Very often, such lists reveal nuggets and shortcomings of said language/system. Yes, even the shortcomings, as something that qualifies as a hack in one language is a boring one-liner in another language, because the task at hand is built in.
