MOD EDIT: Please don't repost old suggestions; come up with your own, or take old suggestions and add your own personal twist to them. Preferably an interesting one.
And only one suggestion per thread (though you can use a broad idea as an umbrella that covers many smaller, but still related, ideas).
Moved to wishlists.
I have some ideas that I have came up with (Stolen from films and other games) Some might be already posted, but I'll just repost them..
Mob Ideas -
Ents - Got this from LOTR. Basically there just like normal trees, but 2x size and have a rotten old look. If you don't attack them, they would not attack you. They would be slow and have 2-3x health as normal mobs, but weak attacks. They would be rare and must un-root before attacking. If there happens to be another ent nearby they would help there kin.
Ghosts - I would imagne them lookling like normal ghost (White robe looking thing) They would be kinda like witches in L4D. They won't like light and anyone near them. They can't be harmed expect by sun light, which won't be any use, because they would be EXTREMELY rare and would be in deed underground cavrens.
More random wildlife - Bears, birds, dogs whatever, you name it..
Horse - For moving around faster.
Carnivorous plants - You have seen them in cartoons and flims. Big plant with a bunch of BIG SAWTEETH. They would eat any living creature. Cow or creeper dosen't matter. It will instantly kill you and you would lose all your stuff and to get them back you have to kill it.
Mummy - Would only be found in deserts. It would look like a.. Mummy and also have flies flying around him.
Telescope - To see futher than actually and to look at stars.
  
  
Latern - It would act as a flashlight and could be hanged on sealings.
Flare - It would light up the nearby area for about 30 seconds making it impossebole for mobs to spawn.
Anvil - For making tools and weapons. Workbench can be left for other stuff (Doors, chest...)
Steel version. Will brake after 50 times of use.
Obsidian version. Does never brake.
Gate - I had a little garden with a fence around it, but I didn't wan't any mob in it so I added a door ,which looked bullsh**. Same as making a door, but with sticks.
Hammer - I don't have a use for it yet..
Weapons and armor -
Warhammer - 2x the damage as a sword, but 2x slower than a sword.
Scimitar - To much Runescape? Anyway, it's a fast curved blade that is weaker than a sword.
Crossbow - Slower, but stronger than a normal bow.