While I second Age of Worms, I have to say my favorite is something I'm borderline obsessed with, but have never gotten a chance to actually PLAY.

XCrawl. It was originally made as a 3.0 setting, but it's our world, if D&D elements were and had always been real. Dungeon Crawls are live Pay-Per-View events, and teams can have corporate sponsors, involve the live audience for morale bonuses, and more.

It's great for a drop game, where you don't need to have any coherent ties from room to room in a dungeon, but would also male for an interesting campaign, as all the game elements outside the individual crawls would be very different from a normal D&D game.

They did a PF1 update with a Kickstarter, called it "Maximum XCrawl", and it was also great. Plus, all the lore and much of the mechanics from the original are still good.