Palm Nailer - Attaches to your air compressor.  Great for tight spaces where you can't swing a hammer, and indispensable if you're suffering from tendonitis or bursitis.

Cordless Drill/Driver - My Milwaukee 14.4 volt cordless survived being totally submerged in a flooded basement.  I let it air out first for a week or two, blew into it with some canned air, and it worked!  The trigger switch jammed after a couple of days, and had to be replaced at a cost of about $40, and the battery was ruined, but I had two spare batteries that had been stored high and dry.

Reciprocating Saw - My Milwaukee Sawzall has been extremely handy in a variety of situations. 

Chop Saw / Compound Miter Saw - Wish I'd gotten one.

Jigsaw - I use mine a lot.

Framing Nailer - Attaches to your air compressor.  You'll use it a lot in the early stages of your project.