PlayerNameCopy

CapsLockCopy is a small client-side mod that lets you copy player nicknames without typing anything.

Point your crosshair at a player and press CapsLock to copy their clean username to your clipboard. If you want the full display name with any prefix or rank formatting, press Ctrl+CapsLock instead. After copying, just open chat and paste with Ctrl+V.
The mod uses ray tracing to find the closest player in your line of sight, up to 128 blocks away within a 5 block wide cone. A short confirmation message appears in chat so you know the copy worked.

Works on any server. No server-side installation required.