A couple more badges. I should probably put these in a Google Doc, since that would be an easier way to distribute them. Maybe I should include Stuart's badges as well, to make everything easy to grab in one go?
For the record, one of my guidelines when deciding what rules category needs an exception, I'm focusing on elements the player interfaces with that are known to be dealbreakers (in other words, I've seen people on forums claim they would or would not play a game with that element.)
I use modified rules for Equipment and Encumbrance. (2eDM mentioned in a comment he's shocked players when they discovered he played encumbrance strictly, but I was still wary of doing a badge for this, until I decided to include equipment in general.)
I use modified rules for Weapons, Armor, and Combat. This badge allows you to warn players that you use extremely detailed replacement rules, or ascending AC in an otherwise straight AD&D 1e game, or d6-only weapon damage (which shocks some people even when you've told them you are playing OD&D.)
I use Psionics, or have modified the psionics rules. Psionics is officially an optional system in most TSR versions of the game, and for some it's a dealbreaker, especially if it replaces magic.
Are there any other rules areas that players are known to have strong opinions about?