I have to agree with quite a few others: A stong staff.
Even better, a magic staff that will collapse on command into a short stick. The stick would be much easier to carry into small spaces where a rogue might need to sneak or hide.
Also, while this isn\'t a weapon per se, I\'d love to have acrobatic skills with witch to avoid all weapons coming at me. Jump, flip, tumble, spring off walls! You\'ll never touch me with that sword/mace/hammer/etc!