- First and foremost: an unofficial remake of the first Half-Life with graphics quality on par with its sequel. For free, no less!
- Even better, the team hasn't received a "cease-and-desist" order; but were instead offered the chance to sell it on Steam! For a low price, even!
- Many awesome moments from the original game return, but the CROWNING moment is a meta example: Black Mesa is a fanmade, updated re-release of the original Half Life using the Source engine. Despite using the same engine as the newer Valve games, it also has many features that those games don't, and is superior in many respects to most of what Valve has made. It was done by a group of fans on their own time.
- Also one for Valve: most video game companies would freak out if a bunch of fans started making a free, improved version of a product that they were still selling for ten dollars. Valve, on the other hand, put it up on Steam for download and said that they were just as excited for the release as everyone else was. A lot of people are taking odds as to whether or not the BM development team gets hired up by Valve.
- Early on a scientist kills a headcrab with a computer monitor. YMMV of course, but you have to give the old guy some credit for showing some real spunk to the eldritch invaders.
- During the chapter "Office Complex" in the original Half-Life, Gordon comes across a cafeteria filled with zombies and headcrabs. Black Mesa maintains the scene, with the only difference being that you can now go into the fight with as many as three security guards at your side, resulting in a hailstorm of bullets as you and your gun-toting companions mow down the horde.
- The booting up of the HEV suit. Even without the Klaxon Beat, the music — along with the list of executed programs and suit functions being turned on — really sends chills up your spine. The HUD slowly flickering on, the chromatic aberration along the health and armor values, and the hands extending in front of the camera in awe of the suit is a testament to how powerful one feels in the Mark IV HEV suit.
- The Lobby Ambush in "Questionable Ethics". A quick but vicious fight against the toughest enemies of the game, which the player is given suitable kudos for surviving by the NPCs.
Scientist: [seeing the carnage] Look what you did!
Security Guard: Holy shit.
Scientist: I...can't believe what you did!
- Keep a guard alive near the end of "Surface Tension": After another guard realizes you're not Marines, we get this exchange
Guard: Jackson? Good God, man, how many lives do you have?!
Jackson: None, if it wasn't for my new buddy here.
- Magnum ammo is a little more plentiful in this game. As such, you'll be using it more often...and every time you kill a hostile Headcrab Zombie or military trooper with it—hell, just firing that hand-cannon, thanks to the updated graphics and sound—will make the player feel powerful.
- Related to that, the satisfaction of plugging one of those HECU Assassins with it and getting the Dead Reckoning achievement is just amazing
- A nod to the opposing forces—they're much deadlier than ever. Examples include...
- Headcrab zombies. Yes, you read that right. If you don't kill them with a headshot, the headcrab will leap off the corpse it was controlling, making you waste extra rounds to kill it for good.
- The Gargantuas are much more powerful this time around—you won't be able to just kill these beasts with a massive stockpile of ammo. You have to use the environmental hazards present to kill them when they show up, and pray you can outrun them long enough to get to said hazards.
- The Tentacles you fight in the Blast Pit are a lot more sensitive to noise and movement.
- The Vortigaunts get a subtle one in the form of their electric bolts—they're much more accurate and quick to charge; if you don't keep moving or put them down fast, you'll get a nasty jolt.
- The Houndeyes' shockwaves do more damage, charge up in less than a second, and blur your screen a little while a ringing noise fills your ears.
- The Ichthyosaurs—they tend to lurk in murky water, so you won't see them until they're practically on top of you. Here's hoping you've got a steady trigger finger and nerves of steel...
- On the human side of things, the helicopter gunships used by the military pack a hard punch, and can take punishment just as well as they dish it out. Bring your heaviest firepower, and find cover.
- The human grunts get this, too. The commandos have all their original strategic maneuvers, plus they can run and shoot, now. Oh, and they're more accurate with their guns. They even have medics!
- Even the allies get some. While they still aren't as strong as the opposing forces, they're smarter.
- Security guards will sneak up on enemies and put up a definite fight, lasting much longer most of the time than they normally did.
- Scientists will use caution and tend to stay out of your way more often so they don't inadvertently die as easily, and they still heal, much better actually.
- Hell, even the Alien Crafts (commonly referred to as Manta Rays or just simply Mantas by fans) are more badass than they were in the original, even though they're still simply just background objects. They don't make the same jittery movements and animations as they did in 1 due to the much more powerful engine, and the dogfights they have in Forget About Freeman are absolutely stunning.
- As of the Surface Tension Uncut update, there's a scene where one chases a military jet fighter (contrary to a previous scene where one was chased by a jet fighter itself) and another where it actually uses its belly cannon and vaporizes a tank that was in the way.