Wheel Truing Stand, Torque Wrench, Zinn and the Art of Road Bike Maintenance, and Bottle Opener.
The tool that makes my life easiest is my portable workstand. After that, it has to be my Craftsman 19v air compressor. You say you can feel a 0.1psi increment? If it makes you happy, I can bump your tire pressure 0.1psi!
Some of the things that make life easier with Euro-X brakes: folded over bit of matchbook for toe-in. 4th hand tool.
At some point, I'm going to invest in a 12v portable power washer. No more lines!
Craftsman cordless inflator with custom head.
Craftsman 13pc hex key set. Although I don't use them all, I feel lost without them.