One item that I created (okay, just tossed a few random thoughts together...) was three throwing daggers with a Metallic Dragon theme.
Each of them had an adamantine blade, with the appropriate metal etched into the blade (creating the shape of an adult dragon of that type).
All had the distance, returning, and keen abilities. Don't remember what I gave them in terms of an enhancement bonus, though.
(I know, the names are kind of hokey...)
Gildentongue: based on gold dragons, it also had flaming burst.
Argenteye: based on silver dragons, it also had icy burst.
Bronzeskin: based on bronze dragons, it also had shocking burst.
I was thinking of tossing in some minor abilities in line with the dragons' special abilities, but never really completed them...