Some power tools will find use all the time.  The better the tool, the easier the work.  I have some very definite opinions about what is essential, and other builders may disagree.  I love my Delta ShopMaster benchtop drill press.  And it finds frequent use.  But I am tempted to say that the band saw is equally valuable.  It finds uses that can never be anticipated.  The same can be said for the Dremel metal disk-belt sander.  I use it all the time.  Below is a listing of useful power tools.  The list is not complete as it does not include a number of tools used on non-aircraft projects.   Even some of these tools will find uses, even the wood shop tools, on a metal aircraft project.