Here's that noir thriller built in the original Half-Life engine you asked for
Blast your way through the neon-drenched city of Prava as you aim to take down its most dangerous gangster.
(Image credit: Valve, Guild of Inventors)
There's been a surprisingly strong run of Half-Life total conversions of late, by which I mean there have been two of them. November brought us Diffusion, a massively ambitious sci-fi adventure with some truly eye-popping environment design, especially considering the age of its tech. Yes, it featured some terrible AI generated text-to-speech. But its creator is working on fixing that and recently revealed some of the human cast for its English dub.
Now, the GoldSrc engine has been given a lick of black paint in the pulp noir thriller The Last Goodbye. Created by Half-Life mod team Guild of Inventors, The Last Goodbye puts you in the stiletto heels of Lucille, a gun-for-hire nicknamed The Banshee who takes on a job to assassinate the deadliest gangster in the City of Prava, a cigar-chomping criminal mastermind known as Bullseye. Between you and your target is an army of pipe-wielding, pistol toting goons desperate to wrap their lips around the barrel of your shotgun.
The Last Goodbye: Act I Trailer - YouTube 
Naturally, though, the game sees you get involved in plenty of scrapes, using pistols, shotguns, and even dynamite to thin the ranks of Bullseye's henchmen. Combat's designed to be challenging, with Lucille lacking the protection afforded Gordon Freeman by his HEV suit. Lucille seems a bit more nimble than Gordon, however, and is also capable of socking enemies in the jaw with her fists.
The trailer above shows the mod in action. I'm a big fan of the Tim Burton-era Gotham City vibe that Prava has to it, a moodily-lit blend of Victorian gothic townhouses and art-deco skyscrapers drenched in sultry neon lighting. I'm also impressed the modders managed to create a convincing looking cat out of GoldSrc-era graphics. Hammering those polygons into place must've taken some effort.
You can download The Last Goodbye on ModDB, although currently the build only includes one of a planned three acts. The modders say that development of act two is "already well under way, with levels and models being prioritised at the moment", and will bring three new enemy types and two new weapons.
And if act one of The Last Goodbye isn't enough to satisfy your cravings, you could always give a shot. While The Chinese Room's sequel isn't a great RPG, it does spin a compelling noir detective yarn, with your Malkavian brain-companion Fabien proving excellent company even in the game's weakest moments. Alternatively, you could just play again, which is never a bad decision.