The very first one, I especially enjoyed the Addon United Offensive a lot.
I really miss the option to set the bodycount to insane in modern CoD titles, btw. I loved it when every single enemy you killed stayed in the level forever. Sure, you needed a lot of RAM for that, but what the hell, just give me the option, ok? =P
Official member of VGC's Nintendo family, approved by the one and only RolStoppable. I feel honored.