Henry said:
Let me second Aetherco's Continuum. To me, it's one of the best time travel games designed, for it's treatment of the way time works, and it's incorporation of all aspects of their rules into the societies that permeate the game.
I disliked their Narcissist product, because I've always been more of a "community" kinda guy, but I liked how they worked two different theories of time travel into the observable rules that the "spanners" like by.
Fascinating to see this- I'm precisely the opposite, the Spanner community described in the base book struck me as totalitarian, monstrously tradition-bound, and beyond loathsome and wrong- while the Narcissists, acknowledging that the timelines they leave behind are typically worse off for it, are still doing things "correctly" since time travel's very existence implies that causality is an illusion (or at the very least a flawed concept). I've been a believer in what the wikipedia article on
the Grandfather Paradox the Relative Timelines theory for years now- to me it seems the only truly logical method of resolution.
And yes, as I mentioned in previous threads on this subject, I use time travel in my games frequently. The most recent use in my Epic game is one the PCs haven't even confirmed is a case of time travel yet; basically, they met a being they knew was from the Far Realm (which is beyond time, and therefore can allow time travel in ordinary reality as a trivial matter) which greeted them as though it already knew them, and thanked them for information they hadn't given it (yet). The point of this is that, unbeknownst to them, that same being is going to appear after they defeat a BBEG critter from the Far Realm that the party's slated to fight soon (presuming, of course, that they don't screw up and lose the fight

). During that meeting, the entity they met will be meeting them for the
first time from its own perspective. I know my players rather well at this point, since this game's been going from 1st level and is now at 25th-26th, so I'm quite confident that at least one of them will divulge precisely the information that led the being to travel to the past and meet them there.
And really, even if it doesn't, the fact that I postulate (in my campaign) the existence of multiple timestreams and multiple "real" futures as possibilities at any given point in time, mean that they do not in fact have to give the entity what they're expected to- the fact that it was even
possible for them to give it means that the entity can have it. It just happened to travel back from the timeline in which they gave it what they were expected to give it.

I love playing with causality this way.