Games the shaped a generation: PC

20. Counter-Strike
Valve | Sierra | 2000

A highly volatile tactical online FPS, pitting terrorists against counter-terrorists in close-quarters battle with modern weaponry

What made it so great?
The anticipation: that seemingly everlasting phase of each round before you encounter an enemy, rapidly checking every dark corner of each room you walk into, listening out for footsteps or the fatal clattering of a flashbang and knowing that death or glory could be less than a second away. No one lasts long in a Counter-Strike firefight and the loser has to sit out the entire round, so the fear of death never quite leaves you - until you're dead, of course.

The dead players sitting out leads to another great - but nerve-wracking - feeling on occasion: your entire team's been wiped out in the opening clash, except you and you don't see any enemy bodies. The burden of wiping out the entire enemy team before they complete their objective falls solely to you and everyone on your team is watching through your eyes, willing you on. And when you do it - pick them off, one by one, through superior tactics and a series of sudden ambushes - a whole chat screen of "played" "nice1" and "gg" awaits you.

Get ready to play
Fair warning: the original Counter-Strike has just had compulsory in-game advertising added to it, so classic maps like de_dust and de_aztec are now adorned with large posters for Portal and Half-Life 2: Black Box. The Half-Life 2-engine remake Counter-Strike Source is free of advertising for now and it's largely faithful to the original.

Been there, done that?
Tom Clancy's counter-terrorist series Rainbow Six hit its peak with Raven Shield: the last of the realistic and tactics-focused editions before it all took a turn for the actiony.