Lamentations of the Flame Princess Weird Fantasy Role-Playing (aka LotFP) is an Old School Renaissance role-playing game whose mechanisms are derived from those of the world's most famous fantasy role-playing game.
Several tropes of said classic role-playing game, however, are given a markedly different treatment in LotFP. To me, the most saliently divergent elements (and the reasons I love this game) are:
1. Although LotFP doesn't provide a default campaign world, the published adventures emphasise a humanocentric setting, as opposed to one with Tolkienesque demi-humans.
2. The rules explicitly advocate a paucity of monsters (there isn't even a bestiary), as opposed to the well-known over-abundance of critters in other OSR role-playing games.
3. The game is exceptionally deadly to player characters.
4. There is a general Renaissance feeling about the published material (art & adventures), as opposed to a pseudo-mediæval one again in most other OSR role-playing games.
Now with regards to point No.4 above, if you say 'Renaissance' you're also saying black powder and firearms. Alas, nor the LotFP core books nor the published adventures contemplate any rules for firearms. I have hence asked James Edward Raggi IV on G+ to give me some guidelines. Not only did he provide some guidelines, but he's also allowed me to post them here!
So, with no further ado, here are James' guidelines:
1d8 damage, ignore 5 points of armour. Rate of fire once/combat.
As a further bonus, a link to the Firearms Fumbles table from the Dungeon of Signs blog.