The godsmen murder mystery. Where you investigate the crime, and interview the suspects, and decide whom to accuse.
Oh yeah that was nice. Whodunit from Oblivion is a bit different though. You can still accuse people from what I remember but you are the killer yourself and just do what you can to get the others killed, no mystery there.
Only problem was I hated oblivion and it's level scaling so much I lowered the difficulty down to easiest, so one shot kill everyone. Even then, it was an AMAZING QUEST.