Forged in the Barrens Cards List & Guide
Swap a minion's Attack and Health.
While it may seem pretty obvious using this on an nerubian egg will kill it and summon the deathrattle.
Just wanted to say here that if you use a temporary attack buff, then use this, the health gets increased permanently.
For example: Using Abusive Sergeant's battlecry on a Chillwind Yeti will give you a 6/5 Yeti for that turn. Using Reversing Switch before the turn ends will leave you with a permanent 5/6 Yeti.