Kid is fussing, so this'll be short. A theory:
Given: super powers originate in the brain.
Evidence: Claire's powers stop working when her brain stem is cut and blocked from regrowing.
Given: Sylar has many powers
telekinesis (stabbing people to ceiling, making puppet Sylar fly away)
time stop (cleared out apartment mighty quick, otherwise!)
"freeze ray"(first serial murder we witnessed, the guy was frozen
Given: The brains of some but not all of those killed by Sylar are missing.
Therefore: Might we assume that whatever Sylar's intial power was. he has devised a way to steal the powers of other superpowered people, perhaps by eating, or otherwise internalizing their brains ? Something to think about.