Rockstar did it with Grand Theft Auto 5. Now a modder has done it with Metal Gear Solid 5: Ground Zeroes.
That modder is "Pao", who tinkered with the PC version of Hideo Kojima's stealth action game and released a first-person mod - all without the help of (official) mod tools.
As you can see from the video below, the mod shifts the camera into a first-person perspective, lending the game a first-person shooter look when Snake aims a gun.
There are issues with the mod, (things vanish when you go near them, for example) but Pao is updating it frequently.
Here's YouTuber BenBlatcher's impressions:
"Not being able to see what's round corners makes things much more tense, and you've gotta be really careful and try and get a good view on things beforehand.
"You've got to rely on your senses a lot more, and it's obvious I wasn't [For example not hearing a truck coming at one point.]"
Give the Metal Gear Solid 5: Ground Zeroes first-person mod a gander over at Nexus Mods.