Of late, I don't know what it is, but I've begun to miss some of the particular features of the D&D of my youth, third edition.
Now not everything, mind you, and not yet implemented in the same way. But I am finding that a nice d20-based skill system, a few simple feats, a saving throw model based on the way one resists rather than the effect one resists against, and even the idea (if not quite the execution) of prestige classes have begun to wander around the distant corners of my mind.
Were you sick of hearing me talk about Clerics yet? In case you weren't, one of the early symptoms of this line of thought came to me when I was reading Luigi Castellani's Dangers and Dweomers, a thought very uncharacteristic of my recent approach: If you were embracing that peculiar D&D henotheism that often rankles me, for instance if you were playing a Forgotten Realms game, it might be an interesting experiment to allow clerics to choose from the appropriate domain spells-- only the domain spells (but perhaps unlike 3.x, all the domain spells, rather than just your choice of two domains from the appropriate god's list.) My brother felt that it restricted the abilities of clerics too much, but I think it'd be an interesting idea, and if not suitable for PCs maybe suitable for NPC priests that are not adventuring, militant clerics.