Black Friday is one of the best times of the year to buy big-screen TVs at discounted prices. Amazon, Best Buy and Walmart are selling their best TVs this weekend. Samsung's Q6F Series QLED 4K UHD TV is discounted to $599.99. Insignia's 50-inch Fire TV is a great entry-level Smart TV with a crisp 4K display and an included remote. Sony's 43-inch Bravia TV is on sale for $368.