If you're asking about other d20 games, one of the more notable additions in several is the defense score (see Spycraft, Star Wars d20, & Wheel of Time), a class level dependent addition to Defence (armor class in D&D) to indicate improved ability to avoid attacks based on experience instead of just equipment. Also, may classes in other d20 games receive bonus feats from a smaller list than the fighter. Spycraft is distinctive in having a very rigid formula for assigning bonues (BAB, Def, Saves, etc) and at what level class abilities are received.
Not sure what you're looking for, but while D&D is my players and my own game of choice, many of the other products have better class design and features (not necessarily more powerful, but often more flavorful.) This is usually due to a more specific nature of the game as opposed to D&D's generic nature.
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