In any case, I decided in my dream that D&D needed more roleplaying elements, so I added this - each character, NPC and monster would have "traits". Those traits could be like, "poor vision" or "sensitive to sunlight" or "easily winded". Anyone who identified one of those traits could then "tag" the trait and choose to either lower the target's AC by 1, or increase their damage to that target by 1.
There would be feats that modified this, for instance rangers could "mark" a tagged target, letting other party-members also take advantage of the tag. Or a ranger could get a feat that let them "auto-tag" their favored prey. These would combo well.
The roll to identify a trait would be a perception roll, which would be a benefit to high wisdom classes, and make paladins and clerics, already identified as "leader" roles, even more useful as a party-leader. Feats to use a trait other than Wisdom would be available, too, as well, as higher levels, getting more than one point advantage from a tag, or using both benefits from one tag. Of course, monsters and NPC's could do the same thing to PC's, and having these traits would provide role-play opportunities to shape who a character is, and how that affects combat.
The funny thing about this dream is, I was telling the new mechanic to an audience at a convention, and the speech came out as if I'd already written it and considered it fully. But, during the process, I was considering new aspects of how it would work and inventing them as I was going along, too - so my creative process not only hands stuff to me when I'm sleeping fully-formed, but it also works to build on the things my sub-conscious has given me.
Also, I'm a big, big, big nerd.