I generally just go for the skins or designs I like most, often to match it up with my character's armor set, not because it looks super rare or unique.
I don't play with random players or try to show off these things enough to warrant super duper rare items, it merely adds to my experience playing the game and makes me enjoy my characters and their appearance more...
The most expensive and elaborate skin item i have is a Obsidian/Orrish earth staff for my elementalist because it just looks so nice with the 15k Geomancer and/or FoW armor...
here for example
I generally try to match my weapons/shields with the armor set of the character I use it on most, sometimes it may require a nice skin, otherwise i just dont care what it is :P Value has no meaning in this decision unless the ideal item is outrageously overpriced