Would work best in a fantasy setting (hence me doing it with NWN) but could work in a sci-fi settitng as well.
Random though: Board game would work quite well, no need to limit this one to the computer
The goal is to create the perfect cup of tea. Of course, this is not easy. Especially when the individual wanting the perfect cup is a rather power mage(warlord/whatever) that's a bit mentaly unstable. And has decided that you will help make this tea or else.
There are four kinds of leaves that are needed for this tea. The first is close by, in the mages garden to be exact. Of course, said garden is the home for a wide range of living, carnivorous, and very hungry, plants.
Another kind is held by a merchant who wants a high price. If you can smooth talk the merchant, you find out he's convinced the mage that the leaf won't taste right if taken by force, and that the merchant fears for his life trying to leave, both from the mage plus some local bandits who have heard of the 'golden' herb the merchant has. Deal with the bandits, and he'll freely give over the herb. Or you can just buy it.
Another herb is found high up in the mountains. A local knows where it is, and can provide that information if you help deal with some poachers. Otherwise the mage know roughly where it is, but you'll have to do quite a bit of exploring.
The final 'leaf' is actualy a flower that only blooms at night. The mage knows exactly where it is too. It also happens to be the hunting grounds of a very nasty nocturnal predator (undead maybe?)
This is where refinment is needed. Not sure on rewards, difficulty, or alternate paths.