Ambiguous Allegiance

This trope occurs when a particular characters allegiance is so unclear as to be a prominent subject of debate among fans. No one is ever really sure who this character is loyal to or if they even have loyalty to anyone. Many things may cause this: Perhaps there's reason to think that the character may not be in control of their own actions, or perhaps they simply change sides as often as you change clothes. Either way, you'll be left wondering whose side they're on for a while. The question may eventually be resolved or it may simply left up to the fans to debate.

Examples of Ambiguous Allegiance include:

Anime and Manga

In Bleach, Gin's allegiance was in question a lot (at first he seemed to be the Obviously Evil Big Bad, then he was revealed as Aizen's minion in a Double Subversion, but in the scenes where he appeared in Las Noches he still seemed rather untrustworthy). Finally it's revealed that Gin had been pulling an epic Batman Gambit where he'd been waiting for the perfect moment to kill Aizen for over 100 years for nothing more than having his thugs attack his Morality Pet (and the fangirls rejoiced). He even almost succeeds.

Literature

Severus Snape from the Harry Potter books. He was a good man, albeit flawed, having kicked the dog a lot. He really was working against Voldemort and was motivated by love for Harry's mother (hence the reason he hated Harry so much; Harry looks a lot like his father, who himself bullied Snape mercilessly). Harry names one of his sons after him and describes him as "the bravest man I ever knew".

Live Action TV

Jason Winkler from House of Anubis was a good guy at first, and then he started to unravel the mystery of Joy Mercer's disappearance. Ultimately, this led him to Victor and the next thing the viewers knew, he had joined Victor's society. This spawned some debate among fans of the series as to whether Jason was being forced to cooperate with the society or whether he had joined of his own free will. (A third theory is that he is the Reverse Mole, pretending to be loyal to the society in order to gather information on them.) Turned out, he was slowly dying and needed The Cup of Ankh to save himself.

Video Games

Axel from the Kingdom Hearts series has no doubt been the subject of such a discussion at least once. Not even his fellow Organization members are entirely sure of where his loyalties lie.

Western Animation

Mr. Krabs from SpongeBob SquarePants