Diaspora: I've written quite a bit about that already. It is certainly my present game fascination. I find the action-economy fascinating. The game doesn't attempt to model everything, instead it creates a system for narrating an effect and mechanically adjudicating that effect, thus high-lighting that a role-playing game is very much a narrative endeavor.
Dungeons and Dragons: Unlike a lot of “RPG-ers of the 80's,” I didn't get my start with D&D; In fact, I played Star Frontiers, Shadowrun, Rolemaster and MERP all before I played D&D. It is still my defacto fantasy system, but even that may not be the case over the coming years.
DVONN: One of my favorite abstract games, DVONN is part of the larger GIPF project. While I'm not going to go into the rules, I can say one of the more interesting aspects of the GIPF Project is the idea of playing the base GIPF game, then forking into another game in which the results determine whether or not you can make the specialized move in the GIPF game.
Diplomacy: I wonder if I'll ever play this game again. It takes a group of 7 players willing to devote an inordinate amount of time to betraying each other. I seem to remember hearing a rumor that JFK told his cabinet that they needed to play Diplomacy. I will look back at the fond memories of everyone ganging up on the player of Germany.
Dominion: I've played quite a bit of this and there are certainly resources available to dive into this most interesting card game.
Dark Sun: Fond memories of struggling for survival in the squelching heat of Athas. I like the struggle for life while deciding to either take the easy path and further destroy the world, or take the harder path by deliberately maintaining the precious life on the planet. And nothing was quite as captivating as Eliziac burning single-handedly destroying an entire encampment of slavers