Illogical items
Some items should only exist in certain sizes
Not a bug, but it bugs me ;)
I found some large boots and they were gnomish large boots. I don't see how that works, unless there's a secret race of giant gnomes somewhere. I'd prefer if such combinations didn't happen. 'gnomish' stuff should always be small, 'trollish' stuff always large, etc., as these prefixes imply the item is intended for the named race/species.
(Found something else, not quite the same thing, but: a "tiny great club". Amused me. My troll kept it to use as a stylish toothpick.)