The "Stick Test" - useful tool or just pointless amusement?

Here's a test to determine whether it's useful: Does it ever get people to change their minds/concede the argument? If yes, it's good. If no, it's useless except for the fun it provides you.

Jayson_Virissimo's comments show one reason why it's a poor instrument: it doesn't actually address any of the arguments you actually want it to.

Another reason is that it's a "virtual" argumentum ad baculum. Because it doesn't actually address your opponent's arguments, the only reason it gives them to agree with you is to avoid (virtual) punishment. If it actually does get them to concede the argument, it might be useful, but be aware that it's Dark Arts at best.

For example, if their argument is that it is impossible to judge another culture's activities as being 'evil', I offer up the idea that it's part of my culture to repeatedly thwap people I disagree with on the head with a stick, and thus they have no justification for telling me to stop.

Not being able to judge another culture's activities as intrinsically evil isn't the same as having to like everything everyone else does.

I don't think your "stick test" is worth anything: the person being hit can invoke desire utilitarianism as their justification and still not claim that your action is "evil".

After we came out of the church, we stood talking for some time together of Bishop Berkeley's ingenious sophistry to prove the non-existence of matter, and that every thing in the universe is merely ideal. I observed, that though we are satisfied his doctrine is not true, it is impossible to refute it. I never shall forget the alacrity with which Johnson answered, striking his foot with mighty force against a large stone, till he rebounded from it, 'I refute it thus.'

If Berkeley's hypothesis is "impossible to refute" or "undisprovable" (as you put it), then how could Johnson have refuted it via his rock kicking experiment? Surely, for all x, if x is unfalsifiable, then x can't have been falsified.