This is the best meter I've ever owned. The display can be read across a dark room, and it include's temperature probe that I find handy when working on temperature alarms.
Black and Decker Gyro Screwdriver
This thing is just plain cool. There's only one button recessed into the rear of the body that activates the gyro when you put pressure on the screw. Then you just tilt the driver in the direction you want the bit to turn. The farther you tilt it, the faster it goes. Plus it's cheap.
I keep this in my clipboard for quick service calls. It's not as cool as the Milwaukee, but it does the job. It's inexpensive but not cheaply made and the display is surprisingly nice.
Milwaukee Cordless Hammer Drill
I have tons of Milwaukee M12 tools, this is my favorite. It can be used as a standard drill, it has a clutch for using it as a screwdriver, and it has a hammer drill function for drilling anchor holes in concrete. Plus it's small enough to fit in my tool bag.
Fluke Tone Generator
A tone generator is crucial for troubleshooting circuits. Attach the generator to a pair of wires, then use the amplifier to track the wire behind walls and above ceilings all the way to the wire's final destination. It's great for identifying all devices connected to a particular security system zone.