Here is the Crash report:
---- Minecraft Crash Report ----

WARNING: coremods are present:
ItemPatchingLoader (ItemPhysic Lite 1.3 mc1.9.jar)
FldLoadingPlugin (FastLeafDecay-1.9-1.6.jar)
CXLibraryCore (cxlibrary-1.0.0.jar)
FMLPlugin (InventoryTweaks-1.61-dev-44.jar)
Contact their authors BEFORE contacting forge

// Everything's going to plan. No, really, that was supposed to happen.

Time: 4/20/16 4:41 PM
Description: There was a severe problem during mod loading that has caused the game to fail

net.minecraftforge.fml.common.LoaderException: java.lang.IllegalAccessError: tried to access field net.minecraftforge.oredict.OreDictionary$OreRegisterEvent.Name from class invtweaks.InvTweaksItemTree
at net.minecraftforge.fml.common.LoadController.transition(LoadController.java:179)
at net.minecraftforge.fml.common.Loader.initializeMods(Loader.java:744)
at net.minecraftforge.fml.client.FMLClientHandler.finishMinecraftLoading(FMLClientHandler.java:307)
at net.minecraft.client.Minecraft.func_71384_a(Minecraft.java:513)
at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:346)
at net.minecraft.client.main.Main.main(SourceFile:124)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:483)
at net.minecraft.launchwrapper.Launch.launch(Launch.java:135)
at net.minecraft.launchwrapper.Launch.main(Launch.java:28)
Caused by: java.lang.IllegalAccessError: tried to access field net.minecraftforge.oredict.OreDictionary$OreRegisterEvent.Name from class invtweaks.InvTweaksItemTree
at invtweaks.InvTweaksItemTree.lambda$oreRegistered$5(InvTweaksItemTree.java:288)
at invtweaks.InvTweaksItemTree$$Lambda$14/344496616.test(Unknown Source)
at java.util.stream.ReferencePipeline$2$1.accept(ReferencePipeline.java:174)
at java.util.ArrayList$ArrayListSpliterator.forEachRemaining(ArrayList.java:1374)
at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:512)
at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:502)
at java.util.stream.ForEachOps$ForEachOp.evaluateSequential(ForEachOps.java:150)
at java.util.stream.ForEachOps$ForEachOp$OfRef.evaluateSequential(ForEachOps.java:173)
at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
at java.util.stream.ReferencePipeline.forEach(ReferencePipeline.java:418)
at invtweaks.InvTweaksItemTree.oreRegistered(InvTweaksItemTree.java:288)
at net.minecraftforge.fml.common.eventhandler.ASMEventHandler_132_InvTweaksItemTree_oreRegistered_OreRegisterEvent.invoke(.dynamic)
at net.minecraftforge.fml.common.eventhandler.ASMEventHandler.invoke(ASMEventHandler.java:49)
at net.minecraftforge.fml.common.eventhandler.EventBus.post(EventBus.java:140)
at net.minecraftforge.oredict.OreDictionary.registerOreImpl(OreDictionary.java:522)
at net.minecraftforge.oredict.OreDictionary.registerOre(OreDictionary.java:469)
at gory_moon.moarsigns.items.ModItems.registerRecipes(ModItems.java:110)
at gory_moon.moarsigns.MoarSigns.modsLoaded(MoarSigns.java:90)
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:483)
at net.minecraftforge.fml.common.FMLModContainer.handleModStateEvent(FMLModContainer.java:560)
at sun.reflect.GeneratedMethodAccessor3.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:483)
at com.google.common.eventbus.EventSubscriber.handleEvent(EventSubscriber.java:74)
at com.google.common.eventbus.SynchronizedEventSubscriber.handleEvent(SynchronizedEventSubscriber.java:47)
at com.google.common.eventbus.EventBus.dispatch(EventBus.java:322)
at com.google.common.eventbus.EventBus.dispatchQueuedEvents(EventBus.java:304)
at com.google.common.eventbus.EventBus.post(EventBus.java:275)
at net.minecraftforge.fml.common.LoadController.sendEventToModContainer(LoadController.java:228)
at net.minecraftforge.fml.common.LoadController.propogateStateMessage(LoadController.java:206)
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:483)
at com.google.common.eventbus.EventSubscriber.handleEvent(EventSubscriber.java:74)
at com.google.common.eventbus.SynchronizedEventSubscriber.handleEvent(SynchronizedEventSubscriber.java:47)
at com.google.common.eventbus.EventBus.dispatch(EventBus.java:322)
at com.google.common.eventbus.EventBus.dispatchQueuedEvents(EventBus.java:304)
at com.google.common.eventbus.EventBus.post(EventBus.java:275)
at net.minecraftforge.fml.common.LoadController.distributeStateMessage(LoadController.java:135)
at net.minecraftforge.fml.common.Loader.initializeMods(Loader.java:742)
... 10 more

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

-- System Details --
Details:
Minecraft Version: 1.9
Operating System: Windows 10 (amd64) version 10.0
Java Version: 1.8.0_25, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 445558376 bytes (424 MB) / 4153815040 bytes (3961 MB) up to 8160477184 bytes (7782 MB)
JVM Flags: 6 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx8G -XX:+UseConcMarkSweepGC -XX:+CMSIncrementalMode -XX:-UseAdaptiveSizePolicy -Xmn4G
IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
FML: MCP 9.23 Powered by Forge 12.16.0.1865 44 mods loaded, 44 mods active
States: 'U' = Unloaded 'L' = Loaded 'C' = Constructed 'H' = Pre-initialized 'I' = Initialized 'J' = Post-initialized 'A' = Available 'D' = Disabled 'E' = Errored
UCHIJ mcp{9.19} Minecraft Coder Pack
UCHIJ FML{8.0.99.99} Forge Mod Loader
UCHIJ Forge{12.16.0.1865} Minecraft Forge
UCHIJ itemphysic{1.3.0} ItemPhysic
UCHIJ abyssalcraft{1.9.1-pre-1} AbyssalCraft
UCHIJ Baubles{1.2.0.0} Baubles
UCHIJ BiomesOPlenty{4.0.2.2012} Biomes O' Plenty
UCHIJ BloodMagic{1.9-2.0.0-33} Blood Magic: Alchemical Wizardry
UCHIJ samsbucketblocks{1.0.1} Bucket Storage
UCHIJ buildingbrickscompatvanilla{1.9-1.4.8} Building Bricks Vanilla Compat
UCHIJ buildingbricks{1.9-1.4.8} Building Bricks
UCHIJ craftablehorsearmour{1.0} Craftable Horse Armour [CHA&S]
UCHIJ craftingcraft{3.0.3} CraftingCraft
UCHIJ cxlibrary{1.0.0} CXLibrary
UCHIJ fastleafdecay{1.6} Fast Leaf Decay
UCHIJ substratum{1.3.0.0} Substratum
UCHIJ foundry{2.0.0.0-alpha1} Foundry
UCHIJ hgp{Release} Horizontal Glass Panes
UCHIJ hopperducts{1.4.7} Hopper Ducts
UCHIJ inventorytweaks{1.61-dev-44-8aeffff} Inventory Tweaks
UCHIJ IronChest{6.0.126.771} Iron Chest
UCHIJ lteleporters{1.1.1} Lemon's Simple Teleporters
UCHIJ lucky{7.1.1} Lucky Block
UCHIJ LunatriusCore{1.1.2.33} LunatriusCore
UCHIJ more{7.0 beta 2} [M-Ore mod](M-Ore 7.2 1.9.jar)
UCHIJ mantle{1.9-0.9.4.jenkins114} Mantle
UCHIE moarsigns{3.0.0} MoarSigns
UCHIJ MoreFurnaces{1.6.0} More Furnaces
UCHIJ morematerials{1.0.20150301.0} More Materials
UCHIJ Morpheus{1.9-3.0.1} Morpheus
UCHIJ MouseTweaks{2.6.2} Mouse Tweaks
UCHIJ fodc{1.8.0} Ore Dictionary Converter
UCHIJ packingtape{0.5.1} [Packing Tape](Packing Tape-0.5.1.jar)
UCHIJ parachutemod{1.4.1} Parachute Mod
UCHIJ planttech{1.4.0} [Planttech](planttech-1.4.0 - 1.9.jar)
UCHIJ progressiveautomation{1.6.41} Progressive Automation
UCHIJ RealisticTorches{1.5.3} Realistic Torches
UCHIJ reinforcedTools{1.4.1} [ReinforcedTools](ReinforcedTools-1.4.1 for MC1.9.jar)
UCHIJ rftools{4.30} RFTools
UCHIJ SophisticatedWolves{3.6.1} SophisticatedWolves
UCHIJ supercraftingframe{1.1.0.38} Super Crafting Frame
UCHIJ tconstruct{1.9-2.2.2.jenkins156} Tinkers' Construct
UCHIJ WorldEditCuiFe{1.0.2} WorldEdit CUI Forge Edition
UCHIJ XaeroMinimap{1.8.7} Xaero's Minimap
Loaded coremods (and transformers):
ItemPatchingLoader (ItemPhysic Lite 1.3 mc1.9.jar)
com.creativemd.itemphysic.ItemTransformer
FldLoadingPlugin (FastLeafDecay-1.9-1.6.jar)
com.olafski.fastleafdecay.FldTransformer
CXLibraryCore (cxlibrary-1.0.0.jar)
cubex2.cxlibrary.CoreModTransformer
FMLPlugin (InventoryTweaks-1.61-dev-44.jar)
invtweaks.forge.asm.ContainerTransformer
GL info: ' Vendor: 'ATI Technologies Inc.' Version: '3.3.11672 Compatibility Profile Context' Renderer: 'ATI Radeon 3000 Graphics'
Pulsar/tconstruct loaded Pulses:
- TinkerCommons (Enabled/Forced)
- TinkerWorld (Enabled/Not Forced)
- TinkerTools (Enabled/Not Forced)
- TinkerSmeltery (Enabled/Not Forced)
- TinkerGadgets (Enabled/Not Forced)
- TinkerOredict (Enabled/Forced)
- TinkerIntegration (Enabled/Forced)
- TinkerFluids (Enabled/Forced)
- TinkerMaterials (Enabled/Forced)ssor

Nothing to do with me, error lies at Inventory Tweaks.
To have the current version of Inventory Tweaks working you need use Forge version 12.16.0.1804 or below, or have a version of Inventory Tweaks compiled for versions above that.

The error lies here:
https://github.com/Inventory-Tweaks/inventory-tweaks/blob/develop/src/main/java/invtweaks/InvTweaksItemTree.java#L288
combined with these changes:
MinecraftForge/MinecraftForge@756c58d#diff-b5ca2d4294ff8ffd8269999435da187eL524