The Post has the latest "oh sweet Christ, what the hell is this thing in my food!?" story, and this one’s a keeper: 27-year-old John Agnesini plans to sue Subway after he found a large serrated knife baked into the bread of his 12-inch cold-cut sub. Agnesini bought it from a Subway on West 35th Street last month during his lunch break: After taking a few bites I could tell something didn't taste right. Then......