Do you see a lot of those in your game? Just sayin' . . .
Vanilla provides rusty iron: dagger, short sword, mace, war axe, bow.
Vanilla does not provide rusty iron: warhammer, battle axe, claymore, long sword.
http://www.uesp.net/wiki/Oblivion:Weapons#Warhammers
Perhaps you are using a mod that provides rusty iron warhammers?