I used to play a heavily house ruled GURPS variant for a long time (alternate attributes, different skill progression scheme, 3-second combat turns with completely different combat mechanics, etc), but a bunch of years ago I decided to return to the roots and get some experience in running vanilla GURPS. After some games, something clicked for me, and I didn’t see a point in all of those house rules anymore – I’ve been running GURPS with very few house rules since then. I don’t think any I use are made out of whole cloth, it’s just simplifications or slight tweaks to published rules. I don’t feel “full” house rules are needed at all, since GURPS offers so many dials you can turn to get the experience you like.
There’s a whole bunch of published rules I don’t use though – but most of them are optional anyway. It would take forever to enumerate all of them because most are just small things, so I’ll just talk about a few notable ones.
The Hit Point System
I only use hit points in pickup games and other games which are intended for a “public” audience. For what I call my “private” games, I use the Conditional Injury rules from Pyramid #3/120. Actually, I’ve used a similar system in the aforementioned heavily modified GURPS variant I used to run. But Conditional Injury is much more elegant. I use such systems because I was never a fan of a death by a thousand rat bites, and sometimes they’re more survivable and feel more “heroic” than the default HP rules, both of which are a plus in my book.
I’ve developed a way to make using Conditional Injury quicker with rapid fire attacks, and I apply one other slight tweak to it: instead of using the Robustness Threshold and Wound Potential tables as published, I just use a straight SSRT progression. Most of my house rules are like that – if possible, try to find an already existing element of GURPS and apply it.
I’ve been using Fantastic Dungeon Grappling ever since it came out, and never looked back. I even use it in my pickup games because it’s extremely simple and easy to understand. There are some situations where it takes a bit adjusting to (a couple of which I’ve outlined here), but I don’t see a reason not to use it in every game ever. Much simpler, and even cooler than the default GURPS grappling rules.
The only house rule I use was borne out of a discussion with the author – stronger characters have a bonus equal to the the ST difference on their attack rolls to break free.
Much like hit points, I only use this in my “public” games and only DF(RPG) ones at that. I vastly prefer magic as powers otherwise, taking elements from both Sorcery and Psionic Powers, though lately I’ve started experimenting with RPM a bit which I’ve otherwise avoided due to it being a completely new system and its tendency to upstage all non-practitioners.
While I like these rules in theory, in practice they suffer from two big problems. The first one is mostly due to my style of play – I need to flip so many switches to make the ships survivable enough and for the combat to work the way I want that I don’t feel the effort is worth it. The second problem is that the combat system is a completely new set of rules which I’ve found many players have no interest in learning.
I don’t run many games involving spaceships or other vehicles, but for when I do I’ve decided to use a modular ship construction system which is a mix of the Modular Mecha article from Pyramid #3/51 and vehicles as characters. As for the combat system – when I ran a mecha game I just treated the mecha as humans and used the default combat rules. Didn’t even bother mapping some of their stats to real world values because it wasn’t relevant. How fast can the mech run? I dunno, it has Move 6, the other mech has 5, you’re not interacting with other combatants anyway. I’ll use something similar for other vehicles if the need arises.
Oh – Conditional Injury is perfect for vehicular damage, and Mailanka has some great crippling rules on his Wiki which make it irrelevant to know which exact systems a vehicle has. He also has a great Action Vehicular Combat set of rules based on chases from Action and the Spaceships combat rules, but I don’t use those because of the same reason I don’t use the Spaceships combat system. Otherwise I would since they fit my requirements perfectly.
As written, the cover rules are very plausible and realistic. Can’t shoot a guy in a body part that isn’t exposed, and an exposed body part suffers a no greater to hit penalty than if it were targeted when its owner isn’t in cover.
Except this creates some perverse gameplay incentives that are noticeable in all but the most grounded, realistic of games. Why take cover so you can’t be hit in your torso armor, which is thicker than your face or hand armor? Why incentivize losing your arm, or skull shots by making the default, easiest target (torso) unavailable? Yes, other hit locations are harder to hit, but they offer commensurate rewards so taking anything but full cover isn’t really a win-win situation as one might expect. Especially against skilled opponents.
I haven’t done anything about this yet because the tug of plausible rules based in reality and my desire for few house rules is strong… but I might just say that any kind of partial covers gives the same penalty to hit all hit locations as it does to hit torso. Like, you don’t need to fully expose your hands and face to shoot, just partially. If your attacker suffers a -2 penalty to hit your torso, but a -4 penalty to hit your arm or a -9 penalty to hit your skull, taking cover is always a net benefit for you which is what I desire from such a defensive option. This is basically a simplification and abstraction of the existing cover rules from Basic and Tactical Shooting.
Active Defense vs Area Attacks
If you’re caught in the middle of an area attack and there is no cover nearby and your step isn’t enough to get you out of it… you’re outta luck. I mostly run cinematic games where this is completely inappropriate. So I mostly just say you can always dive for cover even when there is none… you find some microcover or whatever.
There’s another problem to this – due to the +3 to dodge while diving for cover, characters will generally always succeed at this. Yes, this makes them prone which is its own can of worms. It often turns area effect attacks into non-damaging setups for subsequent attacks. This isn’t a kind of incentive I like, but similar to cover I haven’t done anything about it yet due to my desire to keep changes to a minimum.
Honorable Mention: Unavoidable Damage on Getting Your Natural Attacks Parried
I just ignore this, it doesn’t fit the kinds of games I run. Monsters cheat. Players of characters with claws and sharp teeth like it too.