I did some more "gamemaster rules exception badges", for when you want to advertise that your game is significantly different in one particular area. I wanted to focus only on particularly broad rules; although it would be fun to do a "shields shall be splintered" badge, for example, that's really more specific than is necessary. All prospective players want to know is what they will need to ask questions about for rules clarifications. The two obvious rules areas players would want to know about is character creation and advancement.
My game has different Class, Race, or Ability rules. By itself, it may just mean a few extra classes, or tweaks to the standard classes. Followed by the Improvised badge, this may mean a cliché system (like Risus) instead of classes. Followed by the Gonzo badge, this means weird and varied classes or races, like Arduin Grimoire.
My game has different rules for Experience or Leveling Up. This may mean a "level up every X sessions" rule, or random advancement, or a level cap.