Have You Played... Project IGI?
Go in.
Have You Played? is an endless stream of game recommendations. One a day, every day of the year, perhaps for all time.
I'll be honest: I haven't. But I played the demo so many times over that I feel equipped to reminisce about Project IGI: I'm Going In.
To be clear, IGI had its problems even upon release and I wouldn't recommend anyone return to it today, but it was the closest you could get to Metal Gear Solid V in 2000 - closer than the original Metal Gear Solid. It was a realistic-ish military shooter in which you infiltrated and attacked enclosed, fortified bases, shuffling between patrol routes or crawling through buildings or sniping down upon your hapless foes from a distant ledge. To my young mind, it played like a first-person Commandos and felt part of the same revolution of first-person simulation that included the first Hitman.
In retrospect, it had no mid-mission save and terrible AI. But for the length of the demo, that didn't bother me: it was a first-person game that could be conquered through multiple means, and it had an excellent sniper rifle.
There was a sequel - which I haven't even played a demo of - and then the developer went bust. What a shame.