gtklick is a simple metronome with a GTK interface
and native JACK support. It offers four different sounds, arbitrary meters and beat patterns, and a speed trainer. It's possible to save profiles and restore them later.
Polygnome is a polyrhythmic metronome.
It allows musicians to practice complex polyrhythms,
such as 5 against 4 against 7.
It is capable of doing up to five different meters at once.
It works with the ALSA, JACK, or OSS audio backends.