The only bike lights I am aware of with a really good vertical cutoff are the German street legal lights that Peter White cycles imports. Germany has basically the same sharp vertical cutoff rules for cycle lights as for the low beams of German road legal car lights. As a result their street legal bike lights have the least annoying light patterns for fellow bicyclists and motorists. I believe that German law also limits the power of street legal bike headlights.

Most American bike lights have a round beam which puts out too much light above the horizontal so it is difficult to aim them low enough to not be annoying to others and still have adequate illumination for reasonable speeds. They are equivalent to an automotive high beam.