The item I must have is my handy dandy laminator. I was hesitate to purchase one because I always thought they were really expensive. (Plus there is the cost of the film.) I was happy to find a decently priced laminator on Amazon and the film for under $50! (Plus shipping!) The film is really thick too so I know that it will last for a while.
I also love these Bic Mark It pens. They last most of the year and I use them a lot. Plus they come in a variety of different colors. What teacher doesn't like that?