Dungeons&D6s:Weapons
A dagger is a forearm length weapon. It is a Short weapon, specializing in close fighting. It is able to be sheathed and is able to be concealed, with some effort. Of note, a dagger is a combat weapon. It is not a knife.
Fighter Special: A fighter armed with a dagger is considered to have closed with an opponent with a Medium or Long weapon on the 2nd and subsequent rounds of combat. The dagger wielder always gets a first attack against those opponents. The attack and damage are completely resolved before the opponent gets to attack. Additionally, a fighter wielding a dagger gets a second full attack against foes with Long weapons each round, unless those foes forgo their attack. They don't get a defensive bonus in exchange for that action.