That's a good question as there are so many choices. Personally I use a Hach HQ40d. It's a fine instrument and the electrode (fillable) is the most stable one I have ever owned. It has held calibration for over a month on occasion and that is unheard of. It's got lots of bells and whistles - it actually does DO and conductivity as well as pH, displays calibration parameters each time you calibrate, has ATC, auto buffer recognition and don't even have to write readings down. Each is recorded in memory tagged with time, date, time of last cal, cal parameters, operators name etc and can be transferred to a computer in a format which is readable by Excel (and any other program that can read CSVs) or transferred to a memory stick. The downside is that if you want to own one of these you'd better be prepared to drive a beat up old pickup truck like mine. Priorities!
I couldn't believe that Hanna could sell the little pHep units for as little as they do given all the features they claim so I got one of those and checked it against the more expensive meters from time to time. It actually performs quite well. So that's the one I usually recommend but there are certainly several out there in comparable price range that claim comparable performance. Look for resolution of 0.01 and accuracy of 0.05 (preferably better), ATC (you can live without it and it can fool you but it does make life a little simpler) and automatic buffer recognition. Most of the close to but under $100 meters seem to have most of these.
I used to have to go on about electrodes at length because brewing is quite demanding on the electrode and the electrode is sort of like the speakers in hifi (it doesn't matter how good the electronics are if the speakers are lousy). In recent years there have been many improvements in electrode design which seem to be much more robust (hence the ability of mine to hold calibration for so long).