Flamethrowers man, molotov cocktails, you can still have energy weapons.
And modern day.
I'd rather not do the thing with boss zombies and stuff. I'm a simple man, with simple tastes. When things start waxing complex I begin to long for when they were simpler. Zombies are better when there's one type of zombie(Or a mix of the basic forms. I'm cool with having fast zombies, shamblers, and maybe some kind of zombie that has to be chopped up and burned; but when giant mutant zombies, smart zombies, and stuff like that come in I get a big frowny face), RTDs are better when you just roll, and you don't throw in skills and classes and all of that in it, everything is better when you KISS.
One thing that worries me is that without a main goal other than survival, it will be kind of aimless. I'm hoping a focus on RP will make it easier for people to stay with it for a long time, but I can see why people would want boss zombies, science, and a way to win to keep their interest.
To help remedy this, I'm going to be looking at ways to keep the players on their toes. I'm thinking loud noises attracting zombies will help, leading to situations where it's difficult to hole up for more than a few days before things get too bad to stay, and leading to a lot of intense escape situations where your stronghold is surrounded and you have to fight your way out, find a secret escape route, or LAST STAND FOR GREAT JUSTICE
The more I think about this idea, the more I wish someone else had come up with it so I could be a survivor. Oh well, if it turns out awesome I might even put it in PDF form and let /tg/ see what it thinks.