It depends where you are buying the television. At a garage sale or swap meet, yes you can negotiate the price. At a department store or a big box store, you are not likely to get anywhere negotiating unless you find that the product is damaged. A scratch or something can get you a little discount.
You can try negotiating the price of anything. The problem is that the salesperson might not have that ability or freedom. Did you ever notice how they all have to "go ask a manager" for anything other than a straight sale.