As others have said, Remington 870 Express or Mossberg 500 if buying new. Other options are any used gun in your price bracket such as Ithaca 37, Browning BPS, Winchester 1200 or Model 12, Mossberg 835, or Maverick 88. These latter guns can be found pretty cheap on used racks, particularly the plain barreled ones. I have seen these models in the $250 or even less price range in the last couple of years up to last weekend. These would be pretty much the "ultimate" in beater guns.
