I like to think myself a discerning games player. I explore the far reaches of video games in search of fascinating systems, profound experiences, and deep truths. Also, I cannot stop beaming at Doom II imps dressed up as pirates whose hats drift lazily down to the ground after you blow them away with a flintlock. That's Pirate Doom, a mod giving everything a piratical makeover with twenty-odd new levels, pirate hats, rum, beer, beards, peg legs, cannons, and ripped Monkey Island music.
It's very pretty and cartoony, with silly pirates and lush Monkey Island-y skies, but is a pretty solid pack as well as a bit of a giggle. Though I haven't finished it, the maps seem pleasant, and the replacement weapons strike a nice balance between familiar and new. The shotgun becomes a sawn-off and the rocket launcher is a cannon, for example, but they're not direct analogues and have alt-fire modes like a cutlass slash or barrage of cannonballs.
It does lift music from Monkey Island and sprites from LucasArts' wild west FPS Outlaws but I don't know what you'd expect from pirates.
Pirate Doom is this-a-way. You'll need the GZDoom engine and either a full copy of Doom II or the Freedoom replacement pack for textures and sounds and whatnot. A new version came out earlier this month, adding another map and the sort of change I'm always delighted to find in patch notes:
Added peg legs to Chaingunners
Here's a look at the map added in the latest version, in that merry Monkey Island 'voodoo' style: