I really love playing Burn decks. They're by far my favorite to play. What's more fun than punching your opponent in the face (with Magic cards of course) until they lose? Its also "fair Magic" which I'm very partial to.
When I saw Sword-Point Diplomacy, I immediately thought that this could be a pretty good card for Burn. If you think about it in most Burn builds, its going to do one of three different things every time for each card off the top...1) Give you a card you can play2) Make your opponent lose 3 life 3) Get a land out of your deck so you don't draw it
To add to the benefits of that, if your opponent doesn't give you the card(s), its "loss of life" (your opponent pays the life), not "damage" so it can get around some things that normally lock down Burn, like Worship. Also if they've got Phyrexian Unlife out and are already getting counters, they have to give you the cards because they can't pay the life!
EDIT:As per suggestions, I cut 2 lands (1x Swamp, 1x Mountain) and dropped a few of the 3-CMC cards (Blightning & Sword-Point Diplomacy) to 3 copies each. By doing this, I found room for a playset of Skullcrack, which is a card I totally forgot to include in the decklist (mostly because I didn't have any on paper and I was just going off my actual deck in front of me I assembled).
EDIT #2:Cut the 3xBlightning in favor of 3xKolaghan's Command. As much as I like the card and the flavor of it in the deck, K-Command will almost always be better. Also cut both copies of Rain of Gore & 1 Rakdos Charm from the Sideboard in favor of 3x Leyline of Punishment which is better against Protection from Red stuff and lifegain since RoG doesn't stop Lifelink but the Leyline does.
