It depends on what you want. If you want a shorter game with more strategy, try the QuickPlay Rules or the QuickerPlay Rules. If you want to get into tweaking the game, head to the ZombiesBG Yahoo Group and check out the files and database sections for variants. There are tons of them there.
BAH!! I'm not a fan of Yahoo groups care to post the varients in the varient section here for us lazy fools