The pocket chainsaw is one of the most useful gifts that I’ve ever found, and it’s not even really considered “complex”. The idea is that you can fit it in a case, (which can fit in almost any size pockets, unless they are extremely small), and then from there you can just pop it out and use it. To use it, you simply unravel it and grab the handles. From there, wrap it around whatever surface you are trying to cut, (for instance a tree), and then start to saw! This is not an automatic chainsaw, so you will obviously have to do some work. Even then it’s a really nice gift for really anyone, although it would mostly interest adult males the most. It is cheap too, but the quality of it is unmatched by almost any other pocket tool in the world.
$29 @ ThinkGeek