ametro is a little, simple MIDI Metronome using the ALSA sequencer.
gtklick is a simple metronome with a GTK interface and native JACK support. It's implemented as a frontend to klick.
KMetronome is a MIDI based metronome using the ALSA sequencer. The intended audience are musicians and music students. Like the solid, real metronomes it is a tool to keep the rithm while playing musical instruments.
Maestro Metronome is a cross platform metronome application. It's a very compact metronome easy to use. Maestro Metronome is available in English, Italian and French.
Metronome is a midi based metronome which uses gtk+ for it's user interface. The timing is handled by /dev/sequencer, which should make it very accurate. It has variable speed, variable time signatures, and variable note values.
Simple Metronome (simetro) is a console program that provides basic metronome functions and supports accent patterns.