Here's my 1 and Done Enhancement Shaman! 

Now you may be wondering why it's named as such and here's why. When you play casual duels, if you get offered 4 classes you don't want to play and don't want to lose mmr by auto-retiring, you can simply make this deck if shaman is offered, play your first game which you should win 90% of the time, and you can then retire afterwards and gain 10-30 mmr in the process. 

You can see if you get offered a good passive for shaman like plaguebringer or pillage the fallen, and these will make for a decent run (though I will mention it falls off later in your run unless you get a great second passive). If you hope to legitimately and consistently have good runs in shaman without auto-retiring after the first game I would recommend playing totem shaman instead!

Thanks for reading and feel free to ask questions!