Mount & Blade is a quite obscure game I
ran across by accident. In many respects, it's quite like Oblivion,
except in a zero-fantasy universe and with a better combat
interface (although there are mods for Oblivion that handle that
what makes it exceptional, and hence worth mentioning, is that
you're not playing an adventurer in the way you are in every other
RPG on the freaking planet: you're playing a minor warlord. You get
to collect a (by RPG standards) fairly large group of followers (up
to 50+ if leadership is high, AFAICT) and go do quests as a group.
Also somewhat exceptionally, although not totally uniquely, the game
independently tracks your favour with each lord you encounter, based
on you doing quests for them.
It's really a very original take on the normal open world RPG idea.