I've been using the power probe 2 at work for sometime now. i got to say it is a must have IMO. This isn't just a test light. it allows you to see if a wire is positive or a negitive. You can also send a positive signal or negitive signal through the probe. It's a must when doing alarms or trying to trace a problem. Its been well worth the money and I couldn't see my self using anything else. A regualr test light is useful to a point but the probe allows for so much for when testing wires. it's about 100 bucks which it the norm from the snap on guys. This is not a snap-on product. Check it out at
http://www.powerprobe.com/