At it's hard, Dwarves vs. Zombies (or DvZ) is a roleplaying game at heart. The players all take the role of dwarves and spawn into an area. They are required to gather resources, craft armor, cook cakes, and build up a fortress to withstand the upcoming onslaught of monsters. As the night comes, a horrific event will occur that will kill off some of the dwarves. Sometimes, it is a mighty fire breathing dragon. Other times, it is a horrific plague. I've also seen rat swarms, tornadoes, and a black cloud of pure death. Once a dwarf dies, they come back as a monster. They can choose to be a zombie, skeleton, or creeper. Each of them functions pretty similar to regular Minecraft mobs, except they are controlled by players. Zombies get a powerful regeneration effect. Skeletons can cause a wither effect if they shoot someone. Creepers well...explode. There are even special monsters that will randomly spawn in like the wolverine, super creepers, spider kings, squirds, kraken, and the iron golem. The game can be played, for free, at www.brucesgym.com. (Note that the server IP for Minecraft and for a web browser is the same).
Every week, the creator of Bruce's Gym gets on and does a streaming even of Dwarves vs. Zombies. When the creator is involved, all sorts of new and exciting things can happen. No game is the same. Be warned they do use strong language in the stream. The stream can be found here.
Terra Firma Craft is a mod for vanilla Minecraft. According to it's website, it is 'survival as it should have been'. It definitely does live up to its name. Terra Firma Craft completely changes how Minecraft is played. For instance, a player can't start a new game, and immediately start punching down a tree. First, they have to break the leaves of a tree to collect sticks. Then they collect rocks from the ground and knap them to create an ax head. Combining the ax head with a stick creates an ax. The player can then chop down the tree, causing the entire tree to break, dropping it's logs on the ground. It gets far more complicate and intricate from there.
As the player breaks the stones on the ground, they may find small bits of metal. Using clay and a crafting bench, they can create a clay mold. When cooked in a fire pit (yes, there are fire pits!) it becomes a ceramic mold. The player then heats up the metal till its melting point and the melted metal is stored in a ceramic mold. When enough metal is melted, the resulting liquid must be cooled, then shaped into an ingot using an anvil (or a piece of rock at the beginning of the game). Then the ingot can be shaped into a tool head. Also, the ingot must be at the right workable temperature in order to be shaped. (See the Metals article for temperature details).
Also, animals can't be instantly bred! There are male and female animals. When 'bred' there is a gestational period and after that, a baby animal is created. There are even fruit trees in the game that can be planted and pruned. Agriculture has a lot more crops than vanilla Minecraft, each of which uses a different nutrient from the soil.
All in all, it is a very detailed and complicated mod. As a single player, it was a lot of work to keep myself alive and well fed for the first few portions of the games. Monsters like zombies and skeletons are a lot more dangerous than in vanilla Minecraft (especially with only a knife to protect myself). It is a very fun Minecraft mod if you are looking for something different to try or something more challenging.
That's all for today. Happy gaming.