What are some good Odyssey 2 games?

Hi all! I recently bought a Magnavox Odyssey 2 at a yard sale and it only came with one game, "SHOWDOWN IN 2100 A.D.". I like it but it's probably best played with two people. Can you guys give me some game recommendations? I don't know anything about the Odyssey 2 library. I saw a voice pack on eBay earlier. What games support that and are any of them good?

 

I like UFO and Freedom Fighters. Havent had time to dive into the rest of the ones I picked up yet.