I use a Wittner MT50 metronome. It is pretty easy to use and makes a pleasant "tock" sound instead of an electronic beep. My only complaint about it is that the calibrated so that there are gaps between the settings (example: instead of jumping from 76 to 80, I would like 76, 77, 78, 79, 80...or at least 76, 78, 80). But this seems to be a characteristic of just about any electronic metronome I've seen.
I've tried metronome phone apps. Some of them are very nice, but I don't like having to hunt down my phone, unlock it, and pull up the app—I'd rather just have a dedicated metronome sitting there ready.