Improvised Weapons

Sometimes an attacker doesn’t have a proper weapon available and makes do with something else. The attacker might punch or head-butt a foe, smash a chair over the foe’s head, hurl a rock at it, or clobber it with a tankard.
    Unless the Dungeon Master says otherwise, an improvised weapon has the statistics noted here.

Improvised Melee Weapons

One-handed1d45 lb. or lessNone or unarmed
Two-handed1d86 lb. or more

Improvised Ranged Weapons

When a weapon is used as an improvised weapon, the weapon’s normal characteristics (such as properties, powers, bonuses, and critical hit effects) do not apply. For instance, if an adventurer smacks an adjacent monster with his or her magic bow and scores a critical hit, the bow’s critical hit effect does not apply, since the adventurer is using the bow as an improvised melee weapon.

Published in Rules Compendium, page(s) 272.