Lamentations of the Flame Princess
LotFP is the brutal and wondrous Weird Fantasy tabletop role-playing game born out of love for underground heavy metal, horror literature and film, and in fact all things strange and macabre. Whatever the inspiration of the moment, be it Lovecraft and Barker, Troma and Hammer, Argento and Fulci, the NWOBHM and True Doom, or Ito and Morrison, LotFP's cadre of writers and artists deliver mind-bending and merciless content for your game table.
Rules-wise, LotFP belongs to the "Old School Renaissance" family of games that uses the Open Game License to recreate game rules of the late 70s/early 80s, with LotFP's particular twisting of those rules flattening out the power level a bit and emphasizing a more horrific and go-for-the-throat attitude.
Being part of the Old School Renaissance also means that every LotFP adventure and supplement is readily compatible with over 100 other RPGs, and their support material is readily compatible with LotFP.