You can always count on Lamentations of the Flame Princess to go a direction that you weren't expecting -- and probably tick off a whole bunch of people along the way.
In 2017 they released a free hardcover book of new spells called Vaginas Are Magic. This year's Free RPG Day offering is titled James Edward Raggi IV's Eldritch Cock. Needless to say, this weird dark fantasy/horror mashup is on the NSFW side.
Better Than Any Man was a free adventure released in 2013 meant to introduce people to LotFP's blend of old-school fantasy with Cthulhoid monstrosities, and it's really incredibly well done for something that doesn't cost a penny.
Set in the Holy Roman Empire during the Thirty Years' War, this massive 180-page (!!) adventure is incredibly fleshed out and features a sandbox style that lets the PCs do what they want ... so long as they get it done before the invading army arrives and kills everyone.
After a bunch of retailers and more traditional roleplayers got angry and accused the module of being about killing kids, the Lamentations of the Flame Princess publisher decided to thumb their nose at the naysayers and make a module that's *actually* all about killing kids.
The Doom-Cave of the Crystal-Headed Children is essentially Skyrim with the "kids can die" mod on steroids. If that sounds like something your group would have a good time with, you can grab the PDF of that amusingly offensive adventure for free over here.