[CamerDisco]

PHP Code:

public Action: OnDamage( victim, &attacker, &inflictor, &Float:damage, &damagetype ) {
    new String:sWeapon[64];
    GetClientWeapon(attacker, sWeapon, sizeof(sWeapon));

    if( StrEqual( sWeapon, "weapon_molotov" ) ) {
        damage = 0.0;
        return Plugin_Changed;
    }

    if( StrEqual( sWeapon, "weapon_hegrenade" ) ) {
        damage = 0.0;
        return Plugin_Changed;
    }

    if( StrEqual( sWeapon, "weapon_incgrenade" ) ) {
        damage = 0.0;
        return Plugin_Changed;
    }

    if( StrEqual( sWeapon, "weapon_knife" ) ) {
        damage = 0.0;
        return Plugin_Changed;
    }
    
    return Plugin_Continue;
} 


should work