I stick to the rules by rewriting the rules!

DiyoTweaks is my personal tweak mod that I've been using to make the game more interesting. Some things it makes harder, others easier, and some are just for fun.

As this is my personal mod, the version of Minecraft that it's for is related to my Let's Play series. Some of the tweaks are on by default; others are not. The defaults represent what I feel should happen on a regular server or in the game itself.

What can be tweaked?
Hunger - There are two ways you can go about this: Tweaking and just Disable It

Tweaked hunger can set how much food is depleted for heart healing, maximum hunger bar size, regeneration level, and whether you always regenerate health or not.
Disabled hunger is alpha-style hunger. It has a setting for the maximum amount a single food can heal you.

Crosshair

An alternate crosshair is added for ranged weapons. It looks like a target and can be changed with resource packs. A list exists to add ranged items to it.

Classic Mechanics - Want to bring back that alpha or beta feel and still have your mods work? Now you (somewhat) can!

Revert vanilla armor to protect based on the amount it's damaged. This only affects vanilla armor, not mods.
Zombies drop feathers instead of flesh
Fire will eat forests
TNT explodes when punched

Mob Behavior

Zombies have a few tweaks, including baby spawns, reinforcements, and whether they can set players on fire. This doesn't work at all with Zombie Awareness installed.
Endermen won't pick up blocks
Creepers will choose to go after an attacker if they're closer than the current target
Mob can be jockeys. Slime towers ho!

Gameplay

Nametags have a recipe
Animals drop bones when slaughtered on peaceful
Experience orbs drop from more things. Say... zombies burning in the sun?
Alternatively, experience can be disabled.
Animals drop minimum amounts of leather, feathers, etc
In soviet russia, rotten flesh eats you!
More items are stackable
Poison damage interval
Sugar cane height is configurable. Set it to 20 for towers of sugar!

Rendering

Fancy grass is forced on
The HUD is altered for disabled hunger or experience

If you need pictures, here's a couple:

FAQ
Q: Can I put this in a modpack?
A: Yes. Put it in all the modpacks!

Q: What's the license on this?
A: Public Domain

Q: How did you make this mod?
A: Source code is available on github: https://github.com/mDiyo/DiyoTweaks

Q: Why 1.6.4?
A: I wasn't planning on releasing this mod at first. It's my personal mod, and that comes with whatever version of Minecraft I'm playing on currently.

Q: When will you update to 1.7.2?
A: I will not update to 1.7.2. 1.7.10 is another story however... we'll see when Forge updates.