I've been thinking about this for some time, and Will Robertson seems to have a similar idea to get stuff done by others, rewarding them with reputation.
So, in short: part with your hard-earned reputation to organize a mini-contest with a bounty prize on a topic/package you are interested in -- as Will did, for improving a piece of documentation. It's not like people have a use for their reputation after they gain access to moderation tools, anyway.
To keep the spirit of the SE platform, the contests should be in the form of a question that can be more or less objectively answered. This could be tricky for some tasks, but I think is important.
For fun, there might also be Tikz contests for complex non-trivial drawings, with an award for a clean and efficient solution. Scientific writers and researchers high up in the food chain might find a way to "outsource" the boring work of preparing diagrams to somebody willing to earn some extra rep (not that undergrads are in short supply, but that smells a bit like exploitation to me).
Update: The guys at SO already have something like this -- the competitions are marked with a special tag. They have some ground rules on e.g. how often those should appear, who could ask them, to prevent abuse. See this discussion on meta.SO for some idea how the rules could look like.