.kkrieger
A complete first-person shooter in 96 kilobytes — every asset is computed at launch rather than stored.
Released at Breakpoint 2004 by .theprodukkt, a spin-off of Farbrausch, where it won the sub-96 KB game competition. The executable is under 100 kilobytes, yet the textures, geometry, levels and sound aren't stored in it — they're generated procedurally at startup by the Werkkzeug toolchain. The price is a long load and a hefty memory footprint before you meet the first enemy.
As a technical statement it's hard to top: the same size-coding ethos that drives a 64k intro, dialled up into a playable game. Where heaven7 showed what 64 KB could draw, .kkrieger showed what it could be.