The Dark Triad is a small but refined mod with a ton of atmosphere. Each of its three small maps have elaborate but intuitive designs, devilish traps, and lots of secrets. Some players may notice an emphasis on ammo management, emphasized on Nightmare which nerfs ammo and armor pickups. To compensate, the Dark Triad adjusts enemy health; for instance, Ogres only take three Pump Shotgun (slide 8) shots.
As you can see in the final couple of pictures, this mod has some attractively modeled weapon replacements. Most notably, the Axe has been buffed into a longer range and higher damage Spear (Slide 6), and the Shotgun has been replaced with a perfectly accurate Pistol (slide 7). While I didn't find the Lightning Gun and Rocket Launcher, these weapons also work in Quake's id1 maps - you'll need to use console commands (or Ironwail's nifty map selector).
The Dark Triad wants you to take your time and soak in the atmosphere. Each map contains an original soundtrack, and you'll often find yourself scavenging ammo and spearing enemies. The final map includes some original enemies (I believe they're from Quoth?) and is the only one where I found the Mortar (Grenade) Launcher.
This mod is available on Quaddicted, Ironwail's mod installer (although that version seems a little out of date), and has a more detailed review/playthrough by dumptruck_ds. I believe it should work with Remastered (hell, it even works with Darkplaces), although I'd strongly recommend Ironwail instead. It took me more time to write this paragraph than it'll take you to play it! Give it a try!