It would be nice to have guild quests that explore and practice different aspects of a particular class.

for example:

Gladiator Guild Quest - "Bombshelling" [Req GLD lvl 20]
NPC asks player to help test out a new shield for the guild. You are given a 'key item shield' (which enhances shield-bash stun) and are instructed to head to the arena where you are to practice blocking and shield-bashing vs a group of bomb-type mobs that will explode if not stunned regularly. At the end of the time limit, the special shield is returned and the player is given a reward based on how many bombs are still alive.