C R I T I C A L  S T R I K E
      By Josh Jenks ( Haelyn/Staerfeldt )
        For Smaug 1.4a(probably should work with earlier smaugs)

Intro : This one is really easy. Basically it simulates an
AD&D style type "critical hit". It's very simple and is easily
expandable. One in every twenty swings will result in a critical
hit which results in double damage. 

1.) Open fight.c
2.) Find the following code:
    if ( !wield )       /* bare hand dice formula fixed by Thoric */
	dam = number_range( ch->barenumdie, ch->baresizedie * ch->barenumdie );
    else
	dam = number_range( wield->value[1], wield->value[2] );
And directly after that paste :

/* 
 * Critical Hit Snippet
 *   By Josh Jenks [ Haelyn ]
 */
if ( diceroll == 19 )
{
    act( AT_FIRE, "You critically hit $N!",  ch, NULL, victim, TO_CHAR    );
    act( AT_FIRE, "$n critically hits you!", ch, NULL, victim, TO_VICT    );
    act( AT_FIRE, "$n critically hits $N!",  ch, NULL, victim, TO_NOTVICT );
    dam = dam*2;
}

3.) Now simply recompile, reboot and you're all done. This is, like I said, very simple
but does add a little spice to combat.