In the parallel universe that is Mac gaming, we played Marathon. That was my introduction to first person shooters. Technically it was much like Doom and other 2.5D engines, but it faked a look up/down function. D to look up, C to look down, and V to center view. Kind of awkward, but you do that for a hundred hours and you get used to it.
So that was how I played shooters for years afterwards. One highlight was a LAN party in the computer programming lab, playing Unreal Tournament (1999). Keep in mind keyboard-only was the only way I could play at that time - it was all I’d ever known. I did my best, but the other boys kept besting me using the newer WASD and mouse look technique. That is, until we played a sniper rifles only match.
Well, the thing about a center view key, at least on simple, mostly flat maps is, it sets your altitude at 0°, dead ahead. Which is exactly at the height of the other guy’s head. My previously lackluster keyboard-only technique paid off as I scored headshot after headshot. I leapt ahead and won the match, to the surprise of many.
The last game where I clung to my awkward d-c-v setup was Jedi Knight II: Jedi Outcast (2002). After that I bit the bullet and adapted to WASD like everyone else.