Fudge In Nomine
Several years ago, running an In Nomine PBEM, I realized that there were two things about the In Nomine core system that really bothered me. The first was Disturbance. Typically, a given angel could automatically hear a given level of disturbance out to a certain range, with a very hard dropoff after that. (That is, the range at which he had no change of hearing anything was not much farther than the range at which it was automatic.) Additionally, the range to which a given amount of disturbance could be heard varied widely based on the stats of the angels. I would rather have a system that drops off more gradually (as most perception type things do in reality), and that is based on a simple Perception roll.
My other beef with the system was that how well you did at something was completely random— the "check digit" of the In Nomine system, which is just a d6. I prefer a system where it's based on your success margin, so if you're better at something, you're more likely to have a very good success (as opposed to a barely adequate success) at a given task.
Plus, I just like Fudge. So I did the conversion.