Can anyone tell me what a good gun to buy is for the PS2 and where it can be had for cheap....thank you

The only one to buy is the Namco Guncon. The newest model comes with many of the games like Time Crisis II and Vampire Night. You can also find the original Playstation Guncon around used. I've seen them cheap at places like Game Stop. Both Guncon 1 and 2 will work on the PS2 with the gun games.