They are extremely useful against tough enemies, such as tallboys, clockwork soldiers or large groups of enemies. They are also one of the few offensive items effective against river krusts.
Grenades can be used along with supernatural abilities such as Bend Time and Windblast, allowing Corvo to deflect grenades thrown by enemies and to increase throwing distance, enabling long-range kills.
Similarly, the protagonists can slash at grenades in mid-air or on the ground to drive them away.
Activated grenades thrown at the protagonists by enemies can be picked up and thrown back. Killing an opponent in this fashion in Dishonored will unlock the Back Homeachievement.
In Dishonored 2 and Death of the Outsider, while grenades are being cooked, the dials on them will turn ten times before they explode. For players who prefer no HUD, this feature, together with the increasingly rapid ticking sound, help them judge when to throw the grenades.