In most every system, equipment can be both the most diverse element and one of the more unbalancing ones. A shoulder-mounted rocket in the hands of a five-year-old makes that kid about as dangerous as the military personnel for whom the weapon was intended (if slightly less selective about their targets).
Your PCs are that five-year-old.
The key factor that tends to limit access to items and equipment that would otherwise be unbalancing is the price tag. If the PCs can’t afford it, they can’t get their hands on it, so it’s irrelevant what the damage code or homing qualities of the weapon are.
Unless you give one to your bad guys.
GMs don’t have a cashflow. As lord of your own system, you technically have all the monies, and your NPCs can reap the benefits. GMs who aren’t as familiar with the breadth of a system as their players or who simply don’t have the time to optimize four dozen NPCs to the same extent can be tempted to fill in the gaps with items the NPCs might not otherwise have access to, were the roles reversed.
The general anti-establishment vibe of most tabletop games does typically put the money legitimately in the hands of the enemy. The bad guys build the Death Star. The bad guys have the armada. The bad guys have the black market military-grade tech. In most campaigns, that’s a totally viable decision from a purely in-character perspective.
But, like with a five-year-old, if you bring something to the table, no matter how secure you think it is, count on the kids getting their hands on it the moment your back is turned.
There’s a wonderful line often attributed to kleptomaniacal kender: “whatever is not nailed down is mine – whatever I can pry loose is not nailed down.”
Whether they know it or not, this is one of the many core mantras most of your players live by. Many of them won’t think of it consciously. Some of them will, but it’s the former you have to be careful of.
Those who snatch naturally are the sort who will notice, completely innocently, that the bad guy has exited his airship to fight the party on foot (as honorable villains are sometimes wont to do). The player may even go so far as to calculate the check required to leap from the site of battle to the same hanging rope the villain himself used to descend.
Because ropes, as it happens, go both ways.
The PC could be wanting to use the airship in the combat, firing its cannons at the now-exposed villain, or might instead have decided that the better part of valor is to swoop by, pick up their party members, and rush off to the MacGuffin race, leaving the bad guy stranded where he stands. Either could quickly change the course of not just a session by the campaign as a whole, and not necessarily for the better.
The simple truth is you need to be prepared for every item (and really, every spell or trick) that hits the table to be used by the PCs at some point. If it’s something too powerful for you to feel comfortable with them having, you may want to reconsider using it yourself. Your players are likely to feel jilted otherwise – and they’d be right.
A MacGuffin Device is perhaps the one exception: if it’s the focus of the game, you can play keep-away for months without PCs getting upset due to the simple fact that you’re not using the device/spell/thing directly against them under the guise of fair combat. They know the device/spell/thing is obscene – that’s the whole point.
It’s like giving an item its own plot-armor. Of course, like with a monologue, don’t expect them to sit idly by and not at least try to grab it early. Some actual armor might not go amiss.
Everything else: weapons, vehicles, armor, tools, construction equipment, dangerous hand-eating artifacts, animatronic statues of the villain, all of it; be prepared before it hits the table. Even things you consider just parts of the scenery, like the crane at a dig site or the passing tour bus full of nuns, can quickly shift center-stage if you’re not ready for them. Whatever it is, if you describe it, expect your PCs to try and pilot it.
That means three things for you:
- Know what your items and vehicles do (and don’t do) in specific units. Have numbers. Know the limits. Even if they’re just scratched on the corner of an index card, have them ready, and be prepared to hand them over.
- When it comes to leveling the playing field, focus on skills and abilities as often as you can. Brains are harder to snatch, and mind-control tends to sew up the controller so that they can’t otherwise contribute to the scene, so it balance itself somewhat. That may mean taking more time to build NPCs and doing a bit more research. Trust me, it’s worth it.
- Limit access if you need to to items or vehicles you’re not prepared for the PCs to have. Military-grade equipment can easily have biometric scanners that only let them fire for specific people (and may also check for a pulse, which creates a unique challenge for a PC hoping to swipe it). In low-tech settings, magical items may be soulbonded to individuals and only answer to their command, or require a specific activation phrase before activating.
- Weird stuff can be just as tempting as powerful stuff to your players, and can sometimes be used as a fun decoy. Power is great, but if your bad guy attacks with a fleet of giant robots and one random mechanized penguin for reasons unknown, expect many PCs to go for the penguin first.
Remember, you’re just warding against things that might break the entire game, like stealth helicopters that can teleport and epic swords capable of slaying someone at 50 yards without the courtesy of a saving throw. If your PCs grab the generalissimo’s golf cart and drive it into the heart of his headquarters while Ride of the Valkyries plays on the radio, just let them have the damn thing.
That’s not breaking a game. That’s making the fire better.