I was on rpgnow the other day to pick up a copy of Petty Gods at Tenkar's suggestion (free, incidentally) when I stumbled across Sufficiently Advanced (which also has an SRD).
This game is way, way outside my normal fare (and hence may not be interesting to my typical audience) and yet it seems plausibly awesome.
I guess I would characterize it as a hardish-science transhumanist diceless strategic story game driven primarily by ideological conflicts. That's a mouthful, so let's break it down.
Hardish-science: Written by a physicist, and generally everything here falls under plausiblish. Direct conversion of matter to energy is postulated, and with abundant energy come atomic transmutation (through nuclear processes) and plausible FTL through bent spacetime (both Alcubierre-style warpdrives and wormholes). With FTL comes the possibility of time travel (which is used primarily to explain prescient AIs). It's a bit softer than the sort of grungy, one-system near-future SF I've had on my mind since Schismatrix, but it's within the realm of "plausible given sufficiently-advanced technology". Notably absent are violations of thermodynamics and conservation laws (many of the entries in the Technology chapter include a description of their waste heat) and psionics, though extensive cognitive enhancement and weaponized memetics are present. Full marks from me for averting the Jedi Problem in favor of mentats and cognitae.
Transhumanist: A medium-powered character in SA2 is functionally immortal (immune to aging, capable of regenerating lost limbs), has a neural computer capable of backing up their memories, dermal nanites which provide extensive sensory capabilities, implanted energy weapons comparable to modern antitank artillery, and subdermal armor to match. Massive enhancements are the norm, with characters at the top of the scale capable of generating wormholes, mentally simulating a small city (which does raise the question - can an intellect capable of simulating a city simulate a city containing itself simulating a city containing itself simulating a city containing... ? What about simulating a city containing multiple adversarial intelligence of similar strength?), and surviving reentry naked. Uploaded intelligences and groupminds are supported during character creation. The limits of the flesh are no longer binding.
Diceless: This one's straightforward at least. Character generation is deterministic; you just pick your stats. Conflict resolution is also deterministic, based on the relative stats of the opponents.
Strategic: One trouble with deterministic conflict resolution is that if you go up against a superior force, you will lose. Strategic, then, refers to maneuvering the situation into one which favors your strengths and forces an opponent to rely on their weaknesses. This requires intel about an opponent's abilities, which is fortunately readily available through nanotech, cold-reading social abilities, and some mentat-y story mechanics.
Story Game: Narrative mechanics abound, and the main tradeoff during character creation is that the higher your raw mechanical, technological stat-power, the less of the narrative control currency you'll be able to use. Conflict is also resolved in a very story-game fashion, with each side inflicting complications on the other and then describing the action that resulted in those consequences. I also really like the inclusion of Plots and Projects, which are long-term ways to influence the setting (with potential results including scientific discoveries, building a city, or shifting the beliefs of a population).
Driven by ideological conflicts: In the absence of natural threats on scales smaller than supernovae, conflict (in the narrative sense) must come primarily from interaction with one's fellow posthumans and with oneself. One of the main sets of stats each character has is Core Values, ie beliefs, which contribute substantially to his abilities. Some Core Values are chosen, while others are inherited from a character's home culture. A plethora of sample cultures are presented, ranging from the Cognitive Union (a society of people conditioned through their brain-computers to borglike cooperation; core values Obedience and Order) and Nanori (so full of nanites that most other cultures classify individual Nanori as weapons of mass destruction; CVs Emergence and Evolution) to Oldworlders (space-amish; CVs Tradition and Simplicity). I really, really like a lot of these cultures (and also some of the more minor, cross-culture ideological factions); very Schismatrix, and there are some of these that part of me can point to and say "Forget wizards, I want to be that when I grow up." These cultures are driven into conflict by their differing value-systems, and so too are PCs likely to be motivated against their opponents (and each other) by their value systems. The rules note at one point that PCs are sufficiently powerful that often the question isn't "can we do X?" so much as "how can we do X in a manner in accordance with (all of) our beliefs?"
Overall, I'm pretty impressed. Like Sine Nomine's Stars Without Number, this is definitely a science fiction game written by a well-read fan of the genre for other fans of the genre. Unlike SWN, though, SE2 is essentially optimistic on every level, breaking with both gaming tradition and common science fiction tropes to celebrate a mostly-bright future that feels foreign enough to be plausible.
Other things: as noted on the rpgnow page, this is sort of a beta; the art's not done. There were some typos but nothing Mongoose-grade. The organization wasn't great; I'm not sure starting with character generation was the right choice for a game so off the beaten path, mechanically. I had a lot of questions while building a sample character for the first time which were eventually answered by reading the rest of the book, but which were not immediately obvious. Could use a sort of conceptual glossary up front maybe? The five universes (sort of starting conditions in terms of inter-civilization relations) are pretty good; I really liked The Divide (bit of a spy-thriller milieu) and Sublight. I'm conflicted about the organization of universes vs cultures; universes came first, which meant that I had to infer / gradually pick up data about the civilizations mentioned. This is either a triumph of "show instead of tell" or a failure of organization, and I can't decide which. A number of pieces of very short (almost all <1 page) fiction are present in the universes and civilization descriptions; I enjoyed most of the ones I read, and they contributed to the "showing" of civilizations, but they definitely increased the pagecount by a bit in a book that was already not short for the degree of mechanical complexity in the system. The last 10% of the book is designer's notes, including a chart of "if you alter this subsystem, you should expect changes to cascade to these other subsystems", which is glorious.
Review conclusion: It's been a long time since I gamed, but I kinda want to run this.