Currently, I only want two mods brought into actual Minecraft, SmartMoving and Optifine.
However, I know of someone who is currently making a mod that, in my opinion, is brilliant. It would be an amazing addition to the Vanilla game, when it comes out. Here's a link to his blog about it, if anyone's interested: www.abetterminecraft.blogspot.com
Although I love these mods, I am not sure if I want them to be `added` to Mincraft, the only thing I would change about the current system, is to have MC better integrate with all the mods out there, in other words an API, which is on the way