Rules you ignore/alter.
 

GURPS is a toolkit. It’s not meant for you to use everything in each game. That said, there are some rules that we just don’t like/use. Here are some of ours, and our reasoning behind them. What are yours?

• Increasing the versatility of Side Effect. (B109/P106) Basically, we just use this to turn an Innate Attack into a more-useful version of Affliction. It makes ability-creation much easier and most abilities then follow the same mechanics. Only some abilities require the use of Affliction.
  
• You can’t block bullets/beam weapons with a shield. (B327, 375) Enough examples exists in media of this being invalid. It’s as valid to block a bullet/beam with a shield as it is to dodge them—the same logic applies to both: If bullets/beams are too fast to block, they’re too fast to dodge with human reflexes. Instead of erring on the side of “you can’t do that,” we’re erring on the side of “this will be more fun.”
  This really only tends to come up in Supers games, but even so, we’ve allowed the use in non-supers games.
  
• Allowing Extended Duration on Create. (P92) It’s our opinion that the “creation pool” (P93) is an incredibly poor kludge that just doesn’t work. We allow the addition of the Extended Duration enhancement on Create. While it has potential for abuse, just getting a character with Create past the GM requires extensive work, and the GM has general oversite on the power. And, Extended Duration, Permanent is a pretty huge modifier that counter-balances the need for the creation pool.
  
• Reliable not allowed on ranged attacks. (P109) Contrary to popular belief, Accuracy (B102/P99) is not Reliable (P109) for ranged attacks, it does a slightly-different thing. You can put Reliable on a melee attack—only ranged attacks are forbidden. Accuracy is Reliable with Takes Extra Time.
  Allowing the addition of Reliable on Ranged Attacks to represent increased-accuracy attacks hasn’t negatively-impacted our games at all. That said, changing Reliable to +10% for offensive abilities seems to be a better price-point. We also allow the inclusion of Reliable on Afflictions because otherwise, it’s prohibitively-expensive.
  
• Margin-Based is Awesome! (CotN1; 4) This enhancement is awesome and a blast. If you don’t use it, give it a try. Spoon it right in! How this didn’t make it into PU4 is beyond me.

Re: Rules you ignore/alter.
 

This enhancement seems to give a skill bonus to any skill used with an attack? Overall, I find it unbalanced; if you want more skill with an attack, buy more skill.

Consider: With a 10-pont attack, you can gain +10 to skill for only [5]. That's overpowered. Conversely, with a 100-point attack, each +1 to skill costs [5]. That's underpowered (slightly).

Re: Rules you ignore/alter.
 

You're welcome to your opinion. But, our experience says otherwise.

This is less about the character's skill, and more a reflection that some abilites/attacks are simply more inherently accurate.

Hottie is inaccurate with her fireball ability, but her flame dart is exceedingly accurate. And it's not an aimed accuracy--the dart is just more accurate. They both use Innate Attack (Projectile), so, going by skill she'd be equally accurate with both. The best way to reflect this is to put something, inherent, in the ability. Enter Reliable.

Re: Rules you ignore/alter.
 

Homing or Guided would also do that, wouldn't it?

Re: Rules you ignore/alter.
 

I usually forget the rules I alter/ignore until they come up in play, but there are a few I use:

• Altered trait costs. Per and Will start at 10 rather than basing of off IQ, ST costing a different amounts (usually 5), regrowth costing 10, occasional fiddling with DR and TK costs, having teeth and claws is just a perk. A lot of these are less of rule breaks than before Power Ups 9 came out, and a lot of these have their basis in MyGurps. (holy color change the site got redone).
• Setting the point costs of racial templates to arbitrary(low) amounts. Racial templates are cool, but often they have features that are less than optimal. Lowered costs funnels character points in game encouraged directions.
• Letting people buy invulnerability. Its just comes up too much. I usually give it a range around 200 points to 300 points, and I always make sure that it has caveats, so you aren't actually invulnerable.

Re: Rules you ignore/alter.
 

Nope.

Guided relies on your skill. Basically, it just allows you to avoid range penalties. You can use Long-Range 1 (P108) to move from the speed/range table to long-distance penalties and get the same, general effect.

Homing requires an Aim Maneuver to lock-on before the attack can be made, requires you to buy a sense for the ability, and increase the skill from 10 (13, really). Not even remotely useful or ideal.

Re: Rules you ignore/alter.
 

In quite a different way, and more clumsily.

Re: Rules you ignore/alter.
 

I think it's more of a concession to "the Shield is useless against that", rather than, "you can't react".

Well, that's what I thought. I suppose I could just use damage to shields, without tracking damage.

Re: Rules you ignore/alter.
 

Supers (S78) also introduces "unbreakable shields." So, that is also something to consider.

Re: Rules you ignore/alter.
 

I pretty much always extend the ST damage linearly for high values instead of referring to the damage table--so +8 ST is pretty much always +1d thrust and +2d swing, basically, rather than the numbers slowing down and getting closer to each other as ST rises.

If the game really isn't about challenge and conflict and stuff directly, sometimes I'll skip implementing Rule of 16 for resisted abilities like spells.

I agree with the first poster about adding duration to Create. It just works better that way. If someone wants a permanent Create that creates something easily exchanged for money, that's fine, I can always just make them buy an appropriate level of Wealth to go with it.

I often keep skill points separate from other character points, like the buckets of points pyramid article suggests. It mitigates the 'just take a point in each skill you want, then focus on raising DX/IQ/HT/etc. instead' issue.

I usually don't let people take Weirdness Magnet, Unluckiness, or Cursed. I find trying to balance those as GM is annoying work, trying to make sure they're not too good or too bad for their points. I might allow the 'themed' version of Unluckiness (in the second paragraph of its description) since it feels a little less random-GM-fiat than the other options, but it hasn't come up.

There's probably other stuff I'm not thinking of just this moment.