Boss DB-30 Dr. Beat Digital Metronome
I had an old matrix metronome from the early 1990s that you would dial in the BPM and let it rip.  Your only choice was the click along with the flashing LED.  Well I wanted to get better and decided that keeping a locked down beat was going to allow me to progress but the Matrix wasn't giving me the coaching / audio cues I needed.  The DB-30 does.    I bought this because of the 24 beat variations along with the 9 rhythm types (esp triplets).  This allows me to get back into the beat if I mess up.  With so