In my opinion, Production is the only "shoot what you have" division, whereas shooters in the other divisions buy pistols specifically for competition, so why would you want to buy anything but the most competitive combination? The striker fired pistol fans will be all over me, but this is my list:
Production: DA/SA, 9mm, double stack, semi-auto
Limited/L10: SAO, .40, double stack, semi-auto
Open: SAO, 9mm/.38 Super, double stack, semi-auto, with red dot sight and compensator
Single Stack: .45 1911 (I'm not sure if there's an advantage either way, but some prefer .40)
Revolver: S&W 625 6 shot .45ACP