Grape Shot is a shot type in Empire: Total War. It consists of packed metal balls designed to spread when fired, with the intent of killing and injuring crew.
While Round Shot is meant for the hull and Chain Shot for the sails, grape shot is used to cut down the crew of a enemy ship. Firing several small round balls that disperse, they can be devastating at close range, killing many men at once. They are very effective at lowering morale and disabling cannons. They can be used right before boarding for maximum effect.
Grape shot is perhaps most useful for capturing ships relatively intact (as opposed to trying to destroy them). Grape shot deals absolutely no damage to enemy sails or hulls, killing the crew but leaving ships themselves practically untouched. This is useful when capturing ships to sell, as ships become less valuable the more damaged they are. Conversely, round shot works well with grape shot: a ship with an exposed, damaged hull is much more likely to take heavy casualties from grape shot than one that is relatively undamaged.
Historically, Grape Shot was nearly identical to Canister Shot. However, it consisted of larger metal balls than canister shot, so that it could better penetrate the thick hulls of most ships.