Log:

Description: Initializing game

java.lang.NullPointerException: Initializing game
at uvmidnight.totaltinkers.TotalTinkersRegister.onRegisterPotions(TotalTinkersRegister.java:64)
at net.minecraftforge.fml.common.eventhandler.ASMEventHandler_105_TotalTinkersRegister_onRegisterPotions_Register.invoke(.dynamic)
at net.minecraftforge.fml.common.eventhandler.ASMEventHandler.invoke(ASMEventHandler.java:90)
at net.minecraftforge.fml.common.eventhandler.EventBus$1.invoke(EventBus.java:144)
at net.minecraftforge.fml.common.eventhandler.EventBus.post(EventBus.java:182)
at net.minecraftforge.registries.GameData.fireRegistryEvents(GameData.java:857)
at net.minecraftforge.fml.common.Loader.preinitializeMods(Loader.java:630)
at net.minecraftforge.fml.client.FMLClientHandler.beginMinecraftLoading(FMLClientHandler.java:252)
at net.minecraft.client.Minecraft.func_71384_a(Minecraft.java:467)
at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:378)
at net.minecraft.client.main.Main.main(SourceFile:123)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at net.minecraft.launchwrapper.Launch.launch(Launch.java:135)
at net.minecraft.launchwrapper.Launch.main(Launch.java:28)

A detailed walkthrough of the error, its code path and all known details is as follows:

-- Head --
Thread: Client thread
Stacktrace:
at uvmidnight.totaltinkers.TotalTinkersRegister.onRegisterPotions(TotalTinkersRegister.java:64)
at net.minecraftforge.fml.common.eventhandler.ASMEventHandler_105_TotalTinkersRegister_onRegisterPotions_Register.invoke(.dynamic)
at net.minecraftforge.fml.common.eventhandler.ASMEventHandler.invoke(ASMEventHandler.java:90)
at net.minecraftforge.fml.common.eventhandler.EventBus$1.invoke(EventBus.java:144)
at net.minecraftforge.fml.common.eventhandler.EventBus.post(EventBus.java:182)
at net.minecraftforge.registries.GameData.fireRegistryEvents(GameData.java:857)
at net.minecraftforge.fml.common.Loader.preinitializeMods(Loader.java:630)
at net.minecraftforge.fml.client.FMLClientHandler.beginMinecraftLoading(FMLClientHandler.java:252)
at net.minecraft.client.Minecraft.func_71384_a(Minecraft.java:467)

-- Initialization --
Details:
Stacktrace:
at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:378)
at net.minecraft.client.main.Main.main(SourceFile:123)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at net.minecraft.launchwrapper.Launch.launch(Launch.java:135)
at net.minecraft.launchwrapper.Launch.main(Launch.java:28)

===========================

Mods:
Armory Expansion
Construct's Armory
Just Enough Items (JEI)
Kyth's Overpowered Moss
Mantle
Mekanism
Oreberries
Pewter
PlusTiC
Shadowfacts' Forgelin
Tinkers Construct
Tinkers' MEMES
Tinkers' Modifier Modifier
Tinkers' Tool Leveling
Tool Progression
Total Tinkers
Tweakers Construct

I also had this crash, version 0.4.2, downgrading to 0.3.1 fixed it.

similarity in modlist:
JEI
Mantle
Mekanism
PlusTIC
Shadowfacts' Forgelin
Tinkers Construct
Total Tinkers

Woops... Sorry, should have looked at this a long time ago. this was an error with the modularity code, disabling modules completely just crashed the game. 0.4.2 disabled the experimental module by default. 0.3.1 was before the introduction of the experimental module, which is why that stopped the crash. This was fixed with 0.4.3