My favorite quests in Fallout 3 and New Vegas were the murder mystery quests like "Beyond the Beef" and "One for My Baby" were you have to sleuth for clues on who is committing murder. I also like how some of the quests have a weird twist on why the suspects are killing people, like the cannibals in "Beyond the Beef" or the vampires in "Blood Ties". I like these quests because they feel different cuz they have you taking your time exploring areas looking for clues and they have some puzzle solving in them which makes them feel different from other fallout quests.
What type of quests would you like to see more of in future Fallout games?