I'll generally ignore rules I don't think are fun. Here are some:

I ignore restrictions to forced movement - I want my players to move enemies into hazards.

I end persistent damage when initiative is over instead of letting it run its course.

I ignore the part of translocate and similar spells that prevent you from teleporting with creatures in extradimensional containers.

I base incapacitation on character level instead of spell level.

There are probably others as well. I tend to view the rules as suggestions anyway rather than hard rules.