If you really want to be silly about it, a warmace from Complete Warrior sized up to Large would be a one-handed 3d6/x2 exotic weapon that gives -1 to your AC.
Or for a Dex-focused character, an elven thinblade from Races of the Wild would be a one-handed 2d6/18–20/x2 exotic weapon that can be used with Weapon Finesse.