Theory:Gabriel's mother

- It's not clear whether the ability works in the statement as a whole or in its parts, to affirm either one as fact is speculative.

+ Angela knew who his parents truly were.
+ Elle was shocked upon reading Sylar's file.

- If she had an ability, Samson would've taken it long before he'd marry her.

+ Sylar's mother might have had an ability that Samson already possessed. Telekinesis is a possible candidate, since Sylar has a natural affinity for it.

+ Sylar can take an ability without killing like he did with Elle, why can't Samson?

- Nothing indicates Samson was ever aware that he can take abilities without killing.

- Even if he did, it seems unlikely that he'd take the time and the effort to connect with people in order to have their abilities.

- Samson married her. It seems like that would be precipitated by a considerable period of emotional closeness. Besides, Samson may have just had a preference for killing his targets.

- Sylar is now Nathan Petrelli.

- Sylar's mother is dead. What objects would she have?

- This is likely a loose end, never to be tied up like Caitlin or Kaito's ability.

- Nothing suggests that Samson knows that can be done.

- When Samson tried to take Sylar's abilities, he tried to open his skull, suggesting he either doesn't know he can acquire abilities without killing, or that he can't do it, at least not with his son.