I recently got Shivering Isles and reinstalled Oblivion to play. Along the way I popped in Oscuro’s Oblivion Overhaul (which is tough but vastly superior to the basic game) and Kobu’s Avanced Character System. I also got a “reagents vanish when you harvest them mod”.
But what’s your favorite? What makes the game extra-special to you? Something really nice?