What I expected to happen was for the anvil to break the redstone(dust), powering off the piece next to it.
What actually happened was that when the anvil touched the redstone below it the game crashed!
How to make this crash:
Step 1: Place a piece of redstone.
Step 2: Power the redstone.
Step 3: Drop an anvil on the redstone from at least 1 block above it.
Step 4: Wait for it to come up with the crash report info.