Backfire

When a FIRE monster(s) you control is destroyed and sent to the Graveyard: Inflict 500 damage to your opponent.

Overall a pretty good card with great synergy with Firekings. Running 3 FKHA Garunix all in play, rotating out, you're dealing a minimum of 1000 damage per turn (Yours and Opponents), meaning a win in a minimum of 8 turns, less if your running more (I personally use 2). I personally like it as if I get it early on I'm able to shave away anywhere between 1000-4000 LP between my Onslaughts, Circles, Destruct Potions, Generation Shifts, ETC. Very useful against players with not many anti spell/trap cards.

Kickfire

Once per turn, when a face-up FIRE monster(s) you control is destroyed by a card effect, place 1 counter on this card for each destroyed FIRE monster. During either player's Standby Phase: You can send this card to the Graveyard; inflict 1000 damage to your opponent for each counter on this card.

As with Backfire its a great card for shaving off those extra LP's your opponent may have. Although maxed out at 1000 per turn, and easier to destroy since you have to destroy it on a standby phase