Yea, the Wii controller would work quite well I imagine, being
in a 3-D space and all. You could accomplish it with a mouse quite easily (easy in theory

) too. It's hard to find a mouse on the market nowadays that doesnt have 5 or more buttons plus a scroll wheel. I was wondering how would the avatar's arm know the difference between a forward thrust and upward slice seeing as how your mouse is on a 2-D plane.. you could hold down/release one of those thumb buttons to differentiate between a forward thrust and upward slice when the mouse is moved forward, and so on. You could practically mimic every possible arm movement and therefore weapon angle with the combinations of different buttons. I shouldnt say 'every', but alot, much more than a few scripted button mashing strikes you see nowadays.
Then I thought about waist/head movement since the mouse would be controlling the arm/s for the most part. Maybe they could design some sort of feature where your avatar, when in combat, always tries to keep the enemy in front of him, unless the sprint is held down or something. If not in combat, the mouse controls the head view as you're used to in standard FPS's. The avatar would have an 'area of influence' around him, the size and distance depends on the weapon, that would automatically switch 'battle mode' on when an enemy enters that area, thereby switching mouse control to the weapon and the avatar always facing the enemy automatically. You control body movement direction (legs) with the WASD or arrow keys.
All kinds of different weapons with weaknesses and strengths, sizes, roles, ranges.. it could be done. Now I'm waaayy off the thread title, sorry.