I have two, TWO, things about Doom to show you. This is like being an archaeologist in the jungle and discovering a skellington, but the skellington's heart is still beating and then, oh noes, there's a ball chasing me and I've dropped my hat and give me back my whip Alfred Molina! This Doom reporting is tough work. No wonder all the journalists from that period are scarred and flinch whenever they hear the game's name. For the brave, there are two Doom mashups that you should be excited about.
The first is a known entity, Doom The Roguelike. The top-down hell-fighter was just updated with tonnes of new content: "There are several new special levels paired with the old ones for greater randomness! Visit the Military Base, find Mt. Erebus or feel the dread of Limbo. Along with new special levels, there are new level generators and enhancements to the old ones."
That is exciting, but you're here for something new, and I aim to deliver it like a BFG blast to the face of a Strider. Now you probably thinking: "The Strider is a character from Half-Life 2, and the BFG is in Doom. It's too early to be that drunk, surely?" Well I can drink whenever I damn well please! And, yes, the two are generally from different games, but if you have Garry's Mod then the upcoming gmDoom mod will connect the two in the most remarkable way: "gmDoom is a partial source port of Doom integrated into Garry's Mod 13. Assets are loaded from an IWAD, and no binary modules are required! This addon will be available through the Steam Workshop."
Seriously, watch the video below. This isn't a simple paint job, with the integration bringing the classic Doom UI, weapons, and their chunky blasts into Valve's grubby future. Then, as if to show how easy it all was, it's all flipped around and Doom's monsters are being blasted by Valve's weapons. It's still Valve's levels, but the combination of grimy old school sprites wandering through City 17 just makes it all the more impressive.