I like Shaker furniture, the Japanese katana, and similar things that at first glance seem quite simple. But, a second look will reveal that tremendous effort went into making the item appear to look simple, when in fact it is quite complex.
The above Allen Martin schimmel, a Mike Brooks Carolina trade gun, and similar unadorned long guns with complex architectural details are what truly interest me.
Mike Brooks's Game Creepers rifle that he made for himself, but subsequently sold, is another example.