I have a $250 Fellowes MS-460C shredder that does this well.

Handles 10 sheets in the normal shredder, or spam mail with CDs inside the envelope for the heavy duty shredder. I can throw my junk mail without opening them in the heavy duty shredder entry without worrying about those plastic fake credit cards advertisers sometimes send.

Here's a similar model: http://www.newegg.com/Product/Product.aspx?Item=N82E16846101...