Hello. My name is Alex.Thank you for your question.I will be happy to provide you with information you are seeking for educational purposes only.
Here is the list of the top 12 gauge pump action shotguns according to many reviews (semi-auto shotguns that are in top category are usually sell for way over $500):
1) Remington 870 Express and Express Super Magnum
Remington is currently manufacturing about 30 variations of the gun, starting at $411. The Super Magnum line, which includes shotguns that chamber 3 1/2–inch shells, starts at $462. Remington.com
2) Benelli Nova
Various models range in price from $449 to $569. Benelliusa.com
3) Mossberg 500 (my personal choice, since I own one).
The company offers several series at different prices, but the basic 500 All Purpose starts at $401.Mossberg.com
I wish you the best of luck!