Crossbow for obvious reasons. Stays armed and you can fire it immediately after drawing it. Takes a while to reload.
Longbow that takes longer to arm, but has better range and does a lot more damage. Gets less sneak attack damage than short bow (a bow as long as a person would be hard to fire silently)
In Oblivion they have havok chains hanging from the ceiling in the first dungeon that react to momentum and collide with your character, It wouldn't be much of a stretch to include chain-maces/flails?
It would be extremely hard to do that.
BUT, it wouldn't be very hard to simply apply fixed animations to a chain mace. There's lots of great physics animation programs that can make very realistic results.