I was playing in the latest snapshot, as per usual, when I decided to name on of my baby chickens, the exact name I typed in to the Anvil was "Cluckles/Chuckers ;p", my game then crashed and left me with a crash report, this one attached, I believe it was an issue with the characters used in the name, possibly the "/" or the ";", they may be invalid for some reason, upon launching the game the nametag was in my inventory and could be used as it normally should, it was just the taking the nametag from the anvils output slot that crashed the game