Studio Mama has taken used pallets and turned them into chairs. These would be great with a nice waterproof sealant so you can use them in the yard or the patio.
I may have rec'ed this before; I can't keep track. Anyway, it's a testament to how much I adore this wall unit.
Another pallet chair by Studio Mama. Check this out, you buy the instructions online to make this chair. So you can modify it with a coat of paint or waterproof it. Great for backyard BBQ parties.