This page contains a collection of rules we've developed for our campaign. They're mostly based on the 1st. and 2nd. edition Gamma World rules, but probably could be adapted for later editions. Try 'em out and let us know what you think.
The Combat system we use is based roughly on the AD&D (® TSR Inc.) system. Armor Class, Attacks, Damage, and Hit Points remain the same as in 1st. and 2nd. edition Gamma World. What we've added is the THAC0 score. This stands, like in AD&D, for To Hit Armor Class Zero. This is the number it is necessary for the player get equal or better than on a roll of a 20 sided dice to succed in an attack on a target with an Armor Class of 0. If a target's armor class is higher than 0, that number is subtracted from the Thac0, making a lower, easier number for a combatant to beat.
Unlike AD&D there are TWO types of Thaco in the New West.
GRAND THACO CHART:
Is used in all situations involving hand to hand combat. It also applies in situations where a character want's to touch, grab, or otherwise make contact with an unwilling target. A character's Melee Thac0 is determined by averageing their Strength, Dexterity, and Constitution scores and matching the result on the GRAND THACO CHART.
This is used in long range confrontations, when a character wants to throw or shoot a projectile at a target. It's also used when a character wants to make a grab for something out of the air. Ranged Thac0 is determined by averageing a character's Intelligence, Dexterity, and Perception, and comparing the result to the GRAND THACO CHART.
N.P.C.'s AND THACO:
An N.P.C. creature's melee and ranged Thac0 can be obtained from the GRAND THACO CHART using it's Hit Dice, modified by the mercy or blood-thirstyness of the G.M. if the Hit Dice is a larger number than on the chart.
Every item in the Mutant Bastards Campaign has a Reliability Rating. This measures the object or device's ability to function, as well as it's power to withstand punishment or unusual use. Reliability is checked by rolling a 20 sided dice and successfully matching or going below the object's reliability number. Success means the object performs it's task and is still in good shape. Failure means a malfunction or break occurs. An example would be using a sword as a pry bar to open a rusted door. Along with the Strength check for the character to muscle open the portal, a Reliability Check is rolled for the sword to see whether it snaps from this unaccostomed use. In the case of massive overall damage to a character and their equipment, like being caught in an explosion, for example, a Reliability check would be rolled for each object to see what survives and what's destroyed. If the G.M. wants to assign Reliability Values to new varieties of equipment, they should bear in mind that objects of simpler construction are more reliable than things with complex moving parts. Anything involving electronics, explosives, or chemicals generally has a lower Reliability. As a rough guide, for every Tech. Level over I the device is, subtract 1 from a reliability of 20 if the object is in perfect, just off the assembly line condition. All drugs and chemical devices start at a Reliability of 15, and at an 18 if they are electronic.
Equipment bought at a trading post or in town is generally assumed to be in decent condition, or else the store keeper would have gotten his change in hot lead a while ago. Items found in ruins and buried shopping complexes is a different matter entirely. When an item is discovered, roll 1d10 and consult this chart. The object's condition will affect it's Reliability Score.
Roll: Condition / Reliability Change
1-4: Obviously Broken: Drops to a Reliability Level of 3
5-7: Poor : Reduced to 1/2
8-9: Fair: Reduced to 3/4
10: Good: No Change
In our campaign, we use a creature's Mental Strength as their Morale value. By extrapolating from that we came up with Intimidation.
Sometimes Morale can be used to avoid a fight all together, or to get someone to do what you say. Most denizens of the New West have some sort of routine to put the fear into their fellow beings. To Intimidate a creature a Mental Attack is made, pitting the Intimidator's will against their victim. If the Mental Attack succeeds, the target is scared and will react as the G.M. decides, Some run away, others get real respectful real quick and will do whatever the Intimidator says. If the Attack fails, they may call your bluff and start shootin'. Intimidation is a hostile action, and whether it succeeds or fails, it gives the user a -4 on Reaction Checks with that subject. It's tough to make friends with people you bully. If combat ensues an intimidated creature has a -2 to hit in combat and a +5 to Morale Checks against the Intimidator. Sentient beings use this tactic a lot more than animals and plants, but even some non-sentients use bluff to stay alive. Creatures unaffected by Morale, like Landsharks and Cactisaurus, are impossible to Intimidate. Remember, actual size, strength, and fighting ability don't have as much to do with Intimidation as the effective use of psychological tactics and courage to bluff.
A classic example of Intimidation at work is a good old fashioned Showdown. Two bastards face off in the street, staring each other down and sizing each other up, their hands ready on their shootin' irons. Both sides make a Mental Attack against the other. If both fail, the staredown continues and they make another attempt. If both succeed then Initiative is rolled and they come out blazing. If one side succeeds while the other one fails, the loser fumbles at the critical moment and the winner gets a free shot. As combat ensues the loser faces a -3 penalty to hit, while the winner gets a +3 bonus. These rules work just as well for large groups, in what is known as a "Texican Standoff" in The New West, as well as for lone gun or brain fighters.