What was remarkable about the Benjamite archers who came to David at Ziklag?

Answer: Shot and slung with either hand

These Benjamites, kinsmen of Saul, were archers who could sling stones and shoot arrows with either the right or the left hand.

“Now these were the men who came to David at Ziklag, while he was still banished from the presence of Saul son of Kish (they were among the mighty men who helped him in battle; they were archers using both the right and left hands to sling stones and shoot arrows; and they were Saul’s kinsmen from Benjamin):”— 1 Chronicles 12:1-2 (BSB)