Knocking knuckles was the only greeting we could find that signaled both victory and equality; neither bumper has the upper hand, so to speak.
But many of our readers pointed out that bumping fists may have another superior quality: It’s cleaner than a traditional handshake.

Now scientists in Wales have confirmed what these astute readers already knew. You’re much less likely to pass along bacteria when you bump fists than shake hands or high-five, biologists reported Monday in the American Journal of Infection Control.
The study was small. Only five pairs of people bumped, shook and slapped palms. But the findings were clear-cut. A moderately strong handshake transferred more than five times as much Escherichia coli bacteria onto a recipient’s hand than a fist bump, biologist David Whitworth and his colleague at Aberystwyth University found.
And that strong, sturdy handshake your grandpa taught you was even dirtier. It transferred nearly 10 times more bacteria than a fist bump.