If anyone in your family hunts, a hunter costume is super easyto do. We wore my dads hip waders, camo vest complete with stuffed duck in the game pocket, hat with old duck license attached and, best of all, the duck call, which makes a fantastic sound(especially when you don't know how to use it right!).
If you or anyone you know shows horses, a show outfit makes a great halloween costume.
One of the funniest costumes we ever did was the year my sister went as Peggy Bundy. She wore skin tight black capri pants, a hideous animal print blouse, a super wide red elastic belt, high heeled, open toed and open back shoes in gold and a big bouffant(sp?)wig. Found everything but the wig at thrift stores for less than $10 and the wig was a dollar store $5 special. She used her best whiney/nasally voice and put "PEGGY BUNDY" on her nametag(she wore this to work and was a cashier at the time). It was hilarious and she was ahit with co-workers and the customers!