ROSS is the acronym that has been coined here on TDPRI for the Ridgid Oscillating Sanding Station. Orange and a favorite of everyone who's got one. The sell new at HD for $200, but if you talk to the tool manager and sign up for a HD Credit Card, you can do like me and get a $40 discount, and tear-up the credit card once you've paid it off. It's a great tool for guitar building, and every other kind of woodworking.
Drill Press and Band saw are the other must haves, and a good 1/2" shank router and a router table which you can make yourself, or Grizzly has a great President's Special for a complete table kit for about $120. I generally follow the posters here for their preferred tools, and get them as I can afford them. Most I have have not had the chance to use yet, but soon, I will.