Well, I thought this would be easier than it was...
I want an effect like this, but which I can apply to any stroke:
I tried using stroke arrowheads, but they all seem to start just behind the end of the stroke, so it didn't work:
I tried pattern brushes, but the results weren't clean, and in particular, the arrow tips get distorted if there's any curve at the tip:
How can I add this effect to a stroke in Illustrator CS6 and reliably get a square right-angle point flush with the end of the stroke?
Just saw Scott's answer to Custom stroke caps in Illustrator?. The Art brush trick sadly has the same problem with distorted tips as the Pattern brush option, but the custom arrowhead option looks promising - will add an answer if it works and is possible to snap 100% to the stroke width and tip of the stroke.