Mulitimeter

The multimeter is probably the bench technicians best friend. These instruments can be portable or bench top and range in price from a disposable $10 to over $7000. The older analog meters have all but been replaced with the digital devices and frankly I don't miss them. The analog were much more difficult to read and you always had to be aware of the range setting and the lead polarity. The newer digital meters are multi-ranging so you don't have the fuse issue you used to have. Not to mention bent needles and having to zero the meter before each use.
There is good news for analog fans though, they are affected less by RFI(Radio Frequency Interference). Unfortunately, I've never had an issue with this and I use an EMI receiver to test for radio frequency events rather than a hand-held meter.
The digital meters are also extremely accurate. I prefer the digital LCD over guessing whether the needle is between two points. I use an older Fluke 187. It's not the top of the line and I don't believe they even support that model any more, but I like the abuse it can take and it never complains. I also have the option of an IrDA connection to my PC which is invaluable for data logging on long tests. You can set several parameters and plot curves or graphs over any length of time. That saves me from hand logging test data all day.
The higher end Keithley bench top meters will run into the thousands of dollars but I think they are the best choice for critical measurements. The accuracy is phenomenal and assuming you can pry it from the engineers hands, make circuit analysis much more enjoyable.
The leads used on your multimeter can also play a big part in your measurement success or failure. The spring loaded retractable clip leads are my favorite followed by the extreme point probes depending on the application. I dislike the alligator clip leads as they have a tendency to pop off at the wrong time and land in the wrong place. A good set of leads is a must since chasing an open circuit with a broken probe wire will send you over the edge. Making this small investment and checking them frequently is my best advice.