I've been noodling this idea around for a bit now. Thankfully it's one that requires almost no real effort to implement, and has a pretty easy learning curve for players and GMs. Also, it's probably something that people are doing without realizing it already. Basically I'm going to steal the idea of Aspects from FATE for use with Cypher.
First, a bit of background for those of you unfamiliar with FATE and therefore aspects. From the FATE Core System Rulebook, "An aspect is a phrase that describes something unique or noteworthy about whatever it’s attached to." (p.56) Now in FATE there's different types of aspects; High Concept, Trouble, and then regular aspects. Player characters get one each of the first two and three of the last.
The great thing about Cypher is that your character sentence is basically the character's High Concept. Indiana Jones is a Tough Explorer who Hunts Relics, does exactly what the high concept is intended to do and wrap your character up in a neat little one-line package.
That just leaves a Trouble and however other aspects the GM wants. The Trouble aspect is pretty self explanatory, being a character flaw or such that leads the PC into temptation or bad choices. Think something like Indy's That belongs in a museum! that got him into hot water twice in the first hour of The Last Crusade.
Any other aspects just help fill in the blanks. In Fate they are crucial to other parts of the system, but in Cypher they could be used to hit on character traits that aren't easily defined by Type or Focus abilities. This could be something like Opposable Feet, or something like, Branded by the Devil.
OK, so now that I've laid out what Aspects are let's talk about what they would do in a Cypher System game. It all boils down to two parts of the game: GM Intrusions, and player assets. Now, I'm not proposing that there is anything wrong with GMIs, far from it, it's one of the high water marks for Cypher, but at times as GM I just struggle to do a GM Intrusion that fits the scene. Having a character's Trouble aspect handy would be a great reminder of how to do very character driven and personal GMIs. Indy just can't resist a good adventure to find lost cultural treasures, and protect them from Nazi's after all!
As for assets, I feel like, in my experience, players don't always have good ways to grab assets. They have their skills and effort, and maybe an obvious asset from equipment but there are times I wish that somebody would ask, "Hey, Indy is a Tough Explorer who Hunts Relics, can I gain an asset to figure out if this pedestal that the idol sits on has some kind of trap?" Because A) that would be awesome, and B) I would reply "Hell Yes."
And then there are the weird instances of characters. Characters like the mutant Chimpanzee that I created as a pre-gen for Furry Road and posted earlier this week. As a chimpanzee he has opposable feet, meaning that unlike I silly humans he can easily grab and manipulate things with his feet. Maybe not as well as a human hand, but way better than a human foot. This should count for something, but it's not something easy to quantify as a skill, or even a Type or Focus ability. I even checked the mutations in Numenera and The Strange and didn't find something I liked. I built a custom ability, but I think that just having "chimpanzee" as part or whole of an aspect would probably have worked just as well. In fact I'm going to probably do all the Furry Road pre-gens in this way to help cover all the little bits I cannot otherwise catch mechanically with abilities.
I'm not advocating the creation of actual aspect phrases for Cypher System characters, but treating the character sentence as a kind of aspect and using that as GM to help guide GM Intrusions and assets cannot be a bad thing. Much like the One Unique Thing, Icons, and Fractal Design I think Aspects have potential to inform gameplay in other game systems, or, for GMs and players who like, they can even be lifted directly into other games to help bridge character concept with character rules.