Benjamin had 700 select left-handed soldiers. What could each of them do?

Answer: Sling a stone at a hair

Among Benjamin's 26,000 swordsmen were 700 select left-handers who could each sling a stone at a hair without missing.

“On that day the Benjamites mobilized 26,000 swordsmen from their cities, in addition to the 700 select men of Gibeah. Among all these soldiers there were 700 select left-handers, each of whom could sling a stone at a hair without missing.”— Judges 20:15-16 (BSB)