Invented by: 3Dfx
1st use: Voodoo 5 (2000)
Mainstream use: never
Used for: increasing texture size
Replaced by: DXTC

FXT1 was announced (1999) year later after S3TC as its opensource enhanced rival. It had better max compression ratio 8:1, but was slower and sometimes had lower image quality. FXT1 have also 4 different compression algorithms compared to only one from S3TC. But this was solved by releasing DXTC with 5 algorithms as standard in DirectX 6. 1st card with FXT1 was 3Dfx Voodoo 5 5500 released in year 2000 and that was too late to fight with DXTC supported by many companies and developers. Only one other card supporting it was 3Dfx Voodoo 4 (based on same chipset as Voodoo 5). Support was planned also for unreleased Rampage chip. 3Dfx soon after release od Voodoo 4 bankrupted and later was sold to Nvidia. FXT1 texture compression was forgotten and im not sure if even existed any game with its support (probably not).

More info at:
Wikipedia
IXbtlabs
Firingsquad
3Dfx
Whitepaper (PDF)
Presentation (PDF)
OpenGL
Beyond3D