One of my favorite decks I've made is my burn deck. It's quick and easy. Many burn decks have mana costly cards like Lava Axe. In my opinion 5 damage for 5 mana is not a great deal. Another thing is by the time you've got 5 mountains out 6 7 or even 8 turns may have gone by. With the standards I have of a burn deck 7 turns or more is unacceptable. The average kill time of my deck is 4 or 5 turns or on a good day 3 turns. Another common mistake is having creatures in a burn deck. You need to keep your eye on the prize of killing them not defending yourself. When building a burn deck you want to keep it at 40 cards. The less cards there are the greater the chance you will get what you want.
My Deck

12 Mountains
2 Scent Of Cinder
4 Lightning Bolt
4 Shock
4 Seal Of Fire
3 Incinerate
2 Flame Rift
1 Firebolt
2 Rhystic Lightning
1 Thunderbolt
1 Sizzle
1 Volcanic hammer
1 Fireblast
2 Pyrokinesis

You can kill your opponent in 2 turns by drawing 1st and drawing these 9 cards in this order: Lightning Bolt, Mountain, Scent Of Cinder, Pyrokinesis, Fireblast, Shock, Mountain, Incinerate, Pyrokinesis

Burn Deck Brought to you by
Alex Franceski