Quake 4 Become the Enemy

The Strogg harvest humans: organs, limbs, whole bodies wired into their war machine. Quake 4 makes you find out what that feels like. Mid-campaign, Kane is captured and strapped onto a conveyor, and the game shows the conversion step by step, in full detail, no cutaway. It is the scene people still bring up twenty years later, and it changes how you play: after it, you run faster, jump higher and hit harder, because you are partly one of them now. The first half of the campaign is deliberately slower and heavier, the second half lets you feel the difference. Few shooters commit to body horror this thoroughly.

Unlike Quake II, you are rarely alone. Marines fight beside you, medics top up your health, technicians restore your armor, and they can die if you get careless, so keeping them alive matters. Between firefights you hear them argue and grieve over the radio, which gives the invasion a military-brotherhood feel. The campaign also breaks up the corridors: you pilot hover tanks and mechanized walkers, and man turrets. Your arsenal grows as you go, from an infinite-energy blaster to the Dark Matter Gun, which fires black holes at anything in the way, and weapons pick up upgrades along the route. On higher difficulty, ammo runs short, so every gun gets its turn.