Combat is a tricky subject for roleplaying games. Arguments can break out over how realistic damage should be and how many attacks per round a character should have. Guns and gun-like objects* make it all so much worse. If it’s difficult to explain why the bad guy doesn’t die from being stabbed by a three-foot length of steel, imagine the joys of having the same conversation about an entire clip of 7.62 ammo. If you make guns do realistic damage, your characters will never survive the first session. If you scale down the damage, it will quickly become preposterous as your PCs realize they’re literal bullet sponges.
Then there’s auto fire, which makes the problem more extreme. If your PCs get ahold of weapons that fire more than one bullet per trigger pull,* you’ll have a game balance nightmare on your hands. In one extreme, we have systems like Call of Cthulhu, where auto fire literally counts each bullet in a burst as a separate damage roll. Also, auto fire makes you more likely to hit. Anything not immune to bullets is quickly shredded by damage, characters and monsters alike. At the other extreme are systems like the New World of Darkness, where auto fire is only a small bonus to damage. This becomes absurd as players realize that pulling the trigger twice in single fire mode does more damage than holding it down in full auto.
Ironically, in both systems there’s little reason not to use auto fire at all times. It consumes more ammo, but most roleplaying fights don’t last long enough for that to be an issue. This is because so many games still use D&D style stand and deliver combat, where each player takes a single turn that lasts a handful of seconds. These fights are static. Combatants rarely move except to bring their weapons into range. It’s more than a little silly when you try to visualize it, as if every fight was the shootout at the OK Corral.*
Even guns without auto fire can easily do enough damage to hurt your campaign. It’s difficult to tell a good story when your PCs die in their first fight. By the same token, unless you’re running an absurdist comedy, you probably want bullets to be more than a minor annoyance. One solution is to use a system that properly simulates a gunfight. In real life, the vast majority of bullets never hit their targets. In fact, many are fired into the air for no purpose other than to keep the other guy’s head down. Actual firefights are as much about movement as they are about shooting.
Unfortunately, the only system I know of that does that is Burning Empires, which is firmly in the realm of science fiction. If you know another one, great; otherwise, it might be time to start abstracting your combat. Instead of going into the full round by round fight rules, have the combatants make a single or handful of opposed rolls to decide who wins. You can give out bonuses for superior equipment, better positions, etc. The losers shouldn’t automatically be dead, but they should fail to achieve whatever their objective was.* This won’t work if your players are super into the tactical aspect of combat, but it’s something to consider.
If you thought guns were a problem, just wait until one of your PCs tries to throw a grenade. The mechanics of these little exploding gift baskets are even harder to get right, and the potential for absurdity is that much higher. In D20 Modern and systems like it, it’s easy for a character to be completely fine after a grenade goes off right at their feet. On the other hand, in Star Wars: Edge of the Empire,* a thermal detonator will annihilate the target and anyone standing nearby in a terrible explosion.
Then there’s the question of how to handle the attack roll. Some systems make you hit the target’s normal armor class (AC) or its equivalent, but that doesn’t make any sense. You aren’t trying to bean them with the grenade; you just want to get it in their general area. The logical conclusion is that tossing a grenade into the enemy’s square shouldn’t be that hard, making the attack roll much easier.
While super deadly grenades that are easy to hit a target with might sound the most realistic, they aren’t a good solution. For one thing, they’re a good way to make sure your PCs go into battle armed with nothing but grenades. For another, they still don’t properly simulate how grenades are actually used. Once again, the problem emerges from D&D style stand and deliver combat. Because combatants move in turns, it’s difficult to simulate the mad scramble to get away from a grenade that’s just landed beside you. Some games offer a reflex type save against explosive damage, but if the character doesn’t actually move, it’s hard to imagine how that would manifest.*
One solution is to let characters who make a successful save move a few squares away so they take less/no damage, but this requires movement out of turn, which can get complicated. You can also deny PCs easy access to grenades and other explosives. Fortunately, even in the firearm-loving United States, you can’t just walk into a sporting goods store and buy them. The simplest answer is avoid making the players feel like they need grenades. If you continually hit them with enemies who require mountains of damage to take down, they’ll find a way to get their hands on something that goes boom, no matter what hindrances get in the way.
Instead, make the really difficult combats more about tactics or knowledge than raw firepower. This works especially well in urban fantasy or horror games. The shoggoth is just as immune to grenades as it is to knives. To defeat it, you’ll need to know the counter summoning ritual of Old Babylon.
Much more innocuous than guns or grenades, these pocket computers can still have a huge impact on your game – just not in the combat area. First, characters have constant access to instant communication. Regular* cell phones could already do this, but it’s still something to consider. GMs who are used to a fantasy or historical setting sometimes forget that what one PC knows, the others can all know as well. There’s no high-speed drive across the city to deliver important documents or riding hard for days to warn of an orc invasion.
Ironically, you can also face the reverse problem. If a GM* who is accustomed to a modern setting runs a fantasy game, they sometimes have a difficult time reconciling the fact that medieval PCs can’t instantly pass information to the rest of the party.
More problematic, smartphones now mean everyone* has the internet in their pocket. This can make it difficult to control the flow of information, which is essential for many games, especially horror. Let’s say there was a murder that you want the PCs to find out about halfway through the session. You’ve subtly laid out the clues, and then some clever player announces that he’s looking up any crimes that have ever been committed in this area. You could probably find a reason why the murder wouldn’t show up on a search, but it’ll get old fast if you have to do it more than once.
Also, just about every smartphone has a camera. If you ever run a story that depends on people not believing what a PC saw, it’ll be rather inconvenient when said PC uploads several dozen high quality photos of their experience to Facebook.
On a more psychological level, smartphones make it difficult to create a feeling of isolation, something absolutely essential for horror or thriller games. Even if there’s no useful information to look up, the phone is a connection to other people. PCs who don’t feel isolated are far less likely to be scared of whatever is stalking them. They feel like someone has their back, even if it’s only through a cell tower.
If smartphones become a problem in your game, don’t overuse the “sorry, you don’t have signal” excuse. For one thing, not all your adventures will be in places where that’s credible. For another, PCs will quickly get exasperated with it. Instead, be a little more subversive and use their phones against them. If your setting has magic, there’s no telling what kind of hostile sorcery could be cast through something as personal as a phone. A PC might try to search for haunted house floor plans and come away with a head full of mind destroying secrets that humans were not meant to know.*
Alternatively, tech-savvy enemies could be listening in on the PC’s calls. This is surprisingly easy to do with currently available tech, so there’s no telling what your big bads could have up their sleeve. Use this tactic if you want the PCs to be cautious with their smartphones. They can still be used, but it carries a risk.
Hang on, money exists in lots of settings that aren’t modern; why is it uniquely a problem here? Well, as a society gets more and more technologically advanced, money can buy you more and more power. In a medieval setting, there’s just not that much to buy – 3.5 D&D’s insane gear accessorizing notwithstanding. Unless the PC is planning to hire an army (which comes with it’s own difficulties), a huge pile of money doesn’t make them that much more capable. Your sword can only get so sharp, after all.
However, in a modern society, money can buy all kinds of stuff. Guns, grenades, and smartphones, for a start. As a PC’s wealth increases, the possibilities start to get crazy. Cars, body armor, rocket launchers – all products of modern technology that can belong to your party for the right price. The benefits of gear are also more pronounced in a modern setting. Someone with full plate and a well made sword will have an edge for sure, but it’s nothing compared to the advantage conveyed by a .50 caliber anti-materiel rifle set up two kilometers away from the enemy.
It’s true that most of the really powerful stuff isn’t legal for a civilian to own, but PCs usually have the skills to get around such an obstacle. And that’s not even counting games like Spycraft, where the PCs can probably get access to some really dangerous tech without breaking a single law.
It can also be difficult to keep PCs from accumulating embarrassing amounts of wealth. If they have supernatural powers, they’ll have no problem monetizing them. Just imagine what you could do with a pocket full of urban fantasy wizard spells. Even if the PCs have no magic, they’re probably highly skilled individuals, and it’s not difficult to turn those skills into cash.*
Rather than fighting your PCs over every dollar, the best way to handle money in modern settings is to abstract it. Allow your party to earn a few points of wealth rather than counting dollars. Then you can charge some of that wealth in upkeep for their existing possessions, and you don’t have to figure out exactly how much each item should cost. This eliminates the potential for PCs to build up vast stores of dollars that you don’t have the energy to audit. Once the money is reduced to a manageable level, it works out better for everyone involved.
Of course, if this is going to work, the players have to trust you. In fact, that applies to every item on the list. Abuse usually occurs when PCs feel the GM isn’t being fair. If they’re frustrated with unreasonable difficulties, they’ll respond by arming themselves like crazy. If they don’t think a mystery makes sense, they’ll insist on googling every inane detail just in case. Modern elements can exist without abuse, so long as you maintain investment in your game. It’s remarkable how rarely players will act out in a game they enjoy.