Defence 2, by Neilz. Google defence 2 (first link should be right).
It has the deepest building system that I know of. You have to build a city to keep things running so you can keep defending. Your buildings are the defence.
Wow ybom! That sounds really fun! Your description sounds kind of simalar to Age of the Empires, in the way you build a city. I will have to try it out.
Super Energy Apocalypse - Basically you protect several bases from zombies, and with each base you can pretty much build a city around. They only attack at night so you can actually harm them with spotlights, which was pretty neat I thought.
I have no clue. LOL! ybom is a genius and might know though. LOL! I like that Super Energy Apocalypse. It was fun! Definatley one of my fav TD games as of now.