One of the reasons I love Indie RPGs is that they're more focused than big name RPGs. They don't try to be the "play any genre" game, but rather take a very specific genre and make the rules work extremely well in that genre. Many times these Indie games define their own genres.
Solipsist is a game where consciousness is the only thing that truly exists, all else is illusion created by the consensus beliefs of everyone in the world. The PCs have the ability and the will to override consensus belief, and reshape reality.
That, in fact, is the only game mechanic. And it's diceless.
Solipsist is very much a shared storytelling game, where the narration is mostly taken up by the GM, but players, as they reshape reality, can temporarily narrate the effects of those changes. Since reshaping reality is the only way to overcome significant challenges, players end up making a lot of changes to the ongoing story.
To be a GM in this system means adapting to perhaps wild changes in the game world. If all you've GMed before have been carefully planned out dungeon crawls, you'll find it to be a challenge. On the other hand, if you typically go into an adventure with nothing more than a half a page of notes, you'll do fine.
To be a player in this system means having a degree of control over the story that you probably haven't had before.
PCs in this game are practicing solipsists. A person who not only thinks that they are the only important being in the universe, but have the power to make that the absolute truth.
A character in Solipsist is created with an overriding vision. This is their picture of how the world should ideally be, generally with themselves in the center stage. If they go too far in reshaping reality, they might very well end up in a universe that looks exactly like this, where they are the only conscious being. Everyone else will simply be illusions acting out their part in the solipsist's vision.
A list of obsessions that relate to their vision give the solipsist their drive. Reshaping reality is easier when it will work toward fulfilling an obsession.
Balancing out this awesome power are the character's limitations. These are the human weaknesses that keep the PC from fully committing themselves to creating their own private universe. These might be a fear or insecurity of some sort, a commitment to a person, a cause, or whatever.
Since the only mechanic in the game is reshaping reality, let's look at how it works.
Minor changes to reality don't require the mechanic, as long as the narrator agrees. So if your character encounters a locked door, and needs to get through it, your assertion that she picked up lock picking in college might be a valid way to get through the door.
Major changes to reality, and in any case where the narrator disagrees, require the use of the mechanic. Any reshaping of reality must be in line with the character's vision, backed up by their obsessions, and hindered by their limitations.
The GM sets the difficulty level of any reshaping, and then determines which obsessions and limitations apply. Obsessions and limitations are rated with numbers, and you're looking for a total result of 0. More than 0 means that the character's limitations overrode their obsessions, and the change failed. Less than 0 means that they did too well, and are that m much closer to creating their own private universe and disappearing into it.
Also, all changes to the game world are cumulative. So if a character changes the world in one scene so that she is the President of the United States, that fact will be true in all future scenes until another change specifically erases it. This means a bit of bookkeeping for the GM.
I'm very impressed with Solipsist.
It certainly isn't a game for everyone. In fact, it will probably work better with people who haven't grown up on the standard fantasy RPGs. People who loved Story Engine will get along fine, as long as they don't mind the wildly changing nature of the game world. People who can't get enough of Once Upon A Time will probably love Solipsist, as it plays similar to an RPG version of that storytelling game.
I do admit to a bias in favor of shared storytelling games, because for me that's what role playing games are all about, the shared story. If that sounds like you, you won't go far wrong with Solipsist.
Solipsist at DriveThruRPG.com