AB outs

Maybe you could use it for some comparisons without changing the wiring.
For example from master out via A/B Box to two different active full range systems or from monitor out with cab off through two identical power amps to different cabs.
Never thought about it before, but could work if you have too much time.

You could use one as a 2 in, 1 out guitar switch box. To make it easy to quickly change guitars.