This isn't a very exciting post. It's more for me than for you I guess. I spent quite a bit of time this weekend installing all the wiring in the bedroom. I like electrical work. I have a tool belt dedicated to it, with all the specialty tools laid out the way I like them, although the nail puller pokes me in the ribs.
Here's what's in it:
Machinists hammer - this is just a nice small size, good for putting in staples. The ball-peen end isn't useful, but no sharp claws means fewer chances to take a chunk out of a cable or yourself in a tight spot. I inherited this Craftsman from my granddad.
Nail puller - this little puller is good for staples, for demolition or mistake, although I often use the diagonal cutters or a pair of end nippers for pulling tasks.
Box knife - this is what I use for slitting NM cable and a few other similar tasks. I don't like the cable rippers the contractor types use.
6" Diagonal Cutters - good for cutting the small 10/12/14 gauge residential cable, clipping sheathing off stripped cable, and pulling staples. The trick is to grip the staple with the very tips, right against the framing, with the cutter flat on the wood surface. The handles angle out, and you just press down, levering off the cutter and lifting the staple a little bit. Then either pull it with a claw tool or just repeat a few times until it's out. It's a high leverage, high precision way of removing a staple without nicking the wire.
Needle-nose Pliers - A largish pair. Good for punching out knockouts in metal or plastic boxes. Just hold both handles and use the closed tip like a punch to get started, then grab and twist with the pliers until you win. Also used for forming the loops on the end of wires to attach to screw terminals. You do use the screws, right? Only a lazy jackass would use the push-in spring terminals on the back of receptacles and switches. Screw-clamping backwire is ok, but I don't see that on most devices.
Mechanical Strippers - These are the greatest. They are a total luxury, because you can strip wire with the little cutters with the holes in them, but these make it so quick and easy. Mine are made by Ideal, and I think there are some almost as good ones from Klein. There are some knockoffs, but they stink. These have nice sharp steel blades, and quickly and cleanly strip off the insulation with no nicks. They're great for all kinds of wiring tasks.
Non-contact Voltage Detector - these are really handy for sniffing along wires and finding where there is AC voltage present. Great for trouble-shooting, and it's good to get in the habit of checking everything you're working on before something blows up on you. What? You've never turned off the wrong breaker accidentally? But you can't 100% trust them. Always get a signal from a known-hot wire so you know it works before relying on it.
Neon Light - these old-school indicator lights are handy sometimes. A non-contact tester can only tell you where there is ac voltage, not whether a neutral or ground is really connected. The light completes an actual circuit and so tests both sides of the equation.
Screwdrivers - one of each #2 Phillips and 1/4" straight. There are lots of straight slotted screws left in the electrical trade.
Penlight - I keep a little Streamlight Stylus in my bag. Super handy, and small so you can look inside boxes, conduit fittings, or small holes you drill in the wall to fish wire through. I also wear a LED headlamp a lot. It ensures you've always got a little light on whatever you're looking at, and it comes in especially handy when you're in the basement working in the breaker panel with the main off.