Quest Variety Bonus

[Vlaid]

Some kind of bonus to encourage people to do different quests.

Perhaps the less times/longer it has been since you've done a specific quest you would get some intangible bonus of xp/gold or loot. Might be hard to script but it might help cut down on nightly sahuagin/seers runs or something.

[Kinslayer988]

It is more of a player answer than a DM answer. I would rather see it being player driven than DM driven.

[Stranger]

Doing unusual, uncommon quests is often a reward unto itself in my experience.

[Pup]

Years ago Howland put out a challenge for someone to do ALL the quests at the time.  To my knowledge no one has ever achieved it.  Would be fun to try again.