Play Counter Strike 1.6, with full multiplayer, in the browser
I remember playing one of the early CS betas as a Half-life mod in ~1999.
It was such a huge leap in gameplay and style from anything else out there.<p>Most FPSs up to this point were SciFi based, guns like the BFG and plasma guns. Counterstrike's focus on realism really altered how you connected with the game. Columbine had happened very recently and was still very much in the zeitgeist. There was a very real cultural attack on video games as a scapegoat for the massacre.<p>My friends and I would build CounterStrike maps that were the layout of our highschool and would then run around and shoot each other. This was very taboo at the time. We knew that this would be interpreted as threatening by the powers-that-be at highschool, but it was exciting.