GURPS House Rule: 4d6 for Untrained Skill Attempts

In GURPS, when a character tries something they don’t have a skill for, you usually default to a related skill or attribute with a penalty (often -4 for easy, -5 for average, or -6 for Hard and some VH). This works fine, but it can slow things down. You have to figuring out the right skill being used, checking its defaults, and digging through rulebooks for the exact penalty takes time. The Fantasy Trip has an interesting way to handle untrained use: 4d6

So why not use this in GURPS? If a player wants to try something and doesn’t have an applicable skill, the GM picks the most relevant attribute (DX for physical tasks, IQ for mental tasks, occasionally something like Will or HT for specific cases). The player rolls 4d6 and needs to get equal to or under the attribute to succeed. That’s it. No looking up skills or default penalties.

Critical successes are on a roll of 4, which will be much more rare. Critical failures are on a roll of 17+ will be far more common.

This saves a lot of time, no debating which skill default most fits or where to find the list of defaults. You can still use defaulting to other skills, but only if the player or GM knows for sure what those defaults are, otherwise don't waste the time and just roll 4 dice.

Statistically this is more generous for most skills. 4d6 roll is a bit easier than the standard Average default (-5). For example, with DX or IQ 12, you’ve got about a 22% chance of success, compared to ~16% for a -5 default or ~26% for a -4 default. Due to the way the bell curve distribution works, it ends up being more penalizing for higher attributes over a straight penalty, but I also see that as a feature not a bug.

So anyway, it's a neat quick rule that can save a lot of time and not really mess with balance much.