One of my favorites:
Class changing. Specifically, the way that you can change a character's class mid game, giving you a level 1 character who retains some abilities (typically spells) from the old class, and will now level up quickly in the new class, gaining that class's abilities as well. It is fun being able to quickly level up from 1 later in the game. (I do enjoy class systems that don't do the "level back up from 1" thing, but I enjoy it when they do.)
(Of course, this works best if the game doesn't sabotage it; for example, in Dragon Quest 9, higher level characters get a bigger share of the XP from battles (a mechanic I find backwards and which exacerbates level differences between classes after level 45), and the Gold Box games don't allow multiple level ups at once (XP is wasted in that case). Also, 3rd edition D&D (and Wizardry 8) don't qualify either, as the XP requirements don't reset when you add a new class, so you don't get the fast post-class change leveling that you do in other implementations.)
(By the way, anyone have a link to the "most hated gimmick" topic? I lost it when an unexpectedly deleted topic made the "topics I've posted in" inaccessible past the first page.)
